Patent Application
20140331480
The present invention relates to a method, an arrangement and a combination of components for securely mounting replaceable ground-engaging wear points, called teeth herein, of ground-engaging tools of excavating equipment.
BACKGROUND INFORMATION
Excavating equipment is used in various industries, such as mining, quarrying, dredging, road building, landscaping, commercial and residential building construction, and various other construction industries, for digging holes, trenches, tunnels, etc., for breaking-up, loosening and removing soil, gravel, rocks, ore, coal and other ground materials, and for loading such materials into further earth moving equipment. Such excavating equipment includes hydraulic excavators, backhoes, bucket loaders, skid-steer loaders, bucket and rotary dredgers, earth boring drills, excavation drag lines, cable shovels, face shovels, clam shell buckets, ground rippers and the like. All of such equipment includes a ground-engaging tool, such as a digging or loading bucket in the case of an excavator, backhoe, bucket loader and the like, for example. The ground-engaging tool has a forward edge for cutting or digging the ground, and is further provided with ground-engaging wear points typically called teeth. These teeth are subject to extreme wear, due to digging, scraping and prying in soil, gravel, rocks, broken concrete, and other coarse, abrasive, hard materials. For this reason, the teeth are typically removably mounted on the bucket, so that the teeth can be replaced when they are worn beyond a serviceable range. In this regard, each tooth typically has a tooth socket or pocket therein, which is mounted on a nose piece, which in turn is connected to the front edge of the bucket by welding or bolting. Alternatively, some tooth-mounting nose pieces are formed as a permanent component, being forged or cast together with the front digging edge of the bucket. In some cases, an additional adapter piece is interposed between the nose piece and the tooth, for example in order to use a different brand, size or style of tooth in comparison to the design of the nose piece. The nose piece itself is sometimes also referred to as an adapter or as a shank, on which the tooth is to be mounted. In the present application, the term “nose piece” is used generally, broadly and inclusively to include all manner of known nose pieces, shanks and adapters on which replaceable teeth are to be mounted, and the term “tooth” is used generally, broadly and inclusively to include all manner of known replaceable, ground engaging, wear points of excavating equipment.
A nose end of the nose piece is shaped to mate approximately or coarsely with the interior dimensions and configuration of the pocket in the tooth. The tooth is mechanically secured on the nose piece by a tooth fastener arrangement, of which there are many different types known in the prior art. The tooth fastener arrangement typically includes a fixing pin or clip that extends through a hole provided in alignment through the tooth and the nose piece. This fixing pin and the hole for receiving it may extend transversely side-to-side or front-to-back or upwardly/downwardly through the tooth and nose piece in different designs of fastener arrangements. The fastener arrangement typically additionally includes a keeper or retainer that retains the fixing pin in the aligned holes of the tooth and the nose piece. In this regard, conventionally known tooth fastener arrangements include a flex pin including steel pin members and a rubber keeper, a spring pin, a fixing pin and split washer, a bolt and nut combination, a pin and retainer lock, a horseshoe locking clip, a roll pin, a grooved pin, a crimp-on retainer, a pin and plug combination, and various others. While these fastener arrangements are intended to hold the tooth on the nose piece and transfer digging forces from the tooth into the nose piece (in addition to the force-transferring contact of the nose piece in the tooth pocket), there are always remaining gaps between the tooth and the nose piece in the tooth pocket, and the tooth is always slightly loose on the nose piece. This is true especially after the tooth has been in use for digging, resulting in wear and looseness of the tooth. Thus, the tooth can be felt to “wiggle” slightly on the nose piece, for example pivoting slightly around the fixing pin of the fastener arrangement. Such slight wiggling looseness of the teeth on the nose pieces is presently regarded as acceptable field performance, as long as the fastener arrangement holds the tooth on the nose piece and the tooth is sufficiently supported on the nose piece to withstand the digging forces.
However, whenever the tooth can wiggle or move back and forth on the nose piece, this causes chafing wear of both the nose piece and the interior surfaces of the tooth pocket. As a result, the fit of the tooth becomes ever looser on the nose piece, which causes the wear to progress even more rapidly. Furthermore, when the teeth and bucket (or other ground-engaging tool) are digging in sand, soil or gravel, small abrasive particles of the ground material easily enter the gaps between the tooth and the nose piece in the tooth pocket, and these particles further abrasively accelerate the wear of the nose piece and the tooth pocket. The interior wear becomes especially significant when digging in loose sandy or gritty soil, because the sand or grit gets into the gaps between the nose piece and the interior of the tooth pocket and causes significant interior wear, while the exterior wear of the tooth is less in such soil than in hard rocky gravel or broken rock. Still further, water penetrates into the gaps between the nose piece and the tooth in the tooth pocket, and causes rapid rusting corrosion of the worn metal of the nose piece and the tooth in the pocket. These factors all combine to accelerate the wear and the loosening of the tooth.
Finally, the tooth can become so loose that the fastener arrangement can no longer hold it, for example because the elastic or resilient range of the keeper device does not extend as far as the wear has progressed, so that the keeper loses its resilient keeping function. The fastener pin then falls out and the tooth falls off the nose piece during a digging operation, whereby the tooth is generally lost in the soil or other ground material.
Such teeth can range in size from about the size of a man's fist to about the size of a man's torso, and can range in price from about fifty to several hundred dollars. During each week of full time digging operation, an excavation contractor operating several excavation machines may need to replace several teeth that have been lost or that have excessive interior wear and looseness, so that the costs of replacing lost or worn teeth can become substantial. This is especially problematic when a tooth has become loose and/or has fallen off the nose piece even though the exterior dimensions and configuration of the tooth are still within a serviceable range. Furthermore, if the nose piece becomes significantly worn, then the nose piece itself should also be replaced, which involves a significant replacement part cost and also significant labor costs. The nose piece especially becomes rapidly worn if digging continues after a tooth is lost.
When a brand-new tooth is mounted on a brand-new nose piece or shank on a new excavator bucket, depending on the type and size of tooth, the full exterior wear operating life of the tooth might be expected to be in the range of 1000 to 1500 hours, on average, when digging in a typical mixture of soil conditions, but could be only in a range of 600 to 800 hours when digging mostly in rocky gravel or rocks. The above refers to the exterior wear of the cutting, digging and scraping surfaces of the tooth. On the other hand, under good conditions the interior wear inside the tooth pocket and on the nose piece is generally not expected to be as severe and rapid, so that a nose piece may be expected to have an expected operating life of about 3000 hours as a rough average, with a great range of variation depending on the nose piece type and dimensions, the particular machine, the particular nose piece material, the ground type being worked, etc. A typical excavation machine being operated essentially full time by an excavation contractor in New England might be expected to accumulate about 1500 or 1600 hours of operating or digging time per year. Thus, such a machine might need one or two sets of teeth per year in view of the maximum exterior wear service life. But many teeth that have only about 50% exterior wear are now typically being discarded and replaced with new teeth, simply because of looseness of the tooth on the nose piece due to the interior wear of those parts. If operated further, such loose teeth often fall off anyway if they are not replaced. For example, it has been observed that teeth fall off and are lost after as little as about 400 hours of operation, due to interior wear and looseness of the tooth on the nose piece. For the above reasons, excavation contractors and other excavation equipment operators are suffering significant additional costs in replacing teeth that have been lost due to falling off, or that have become too loose on the nose piece due to interior wear, even though the exterior of the tooth would still have provided additional service life.
It has thus long been desired in the field of excavation, to provide an arrangement and/or method by which a replaceable tooth can be secured on a nose piece in such a manner to avoid the wiggling looseness of the tooth on the nose piece as described above, to avoid interior wear of the tooth pocket and the nose piece, and preferably to avoid the penetration of sand or other grit and water into any gaps between the nose piece and the tooth pocket. The prior art has generally tried to increase the security and improve the ease of installation of the tooth fastener arrangements, which has given rise to many different styles of fastener arrangements as mentioned above. Those approaches, however, do not resolve or even address the above mentioned problems of interior tooth pocket and nose piece wear, looseness of the tooth and penetration by grit and water. It is also conventionally known to provide a dirt shield collar around the base of an adapter to keep dirt out of or away from a receiving socket for the adapter, and/or to provide a weld bead to secure an adapter in a socket, or to provide an o-ring seal between a tooth pocket and a nose piece in order to try to keep dirt from entering the pocket. Such efforts have only been partially successful at addressing the above problems, so that further improvements are desired.
In view of the above, it is an object of the invention to provide a method, an arrangement, and a combination of components for securely mounting a replaceable ground-engaging wear point or tooth on a tooth-receiving nose piece of a powered ground-engaging tool such as a bucket of excavating equipment. It is a particular object of the invention to fill and seal existing gaps between the nose piece and the interior of a tooth pocket so as to prevent the penetration of grit particles and water. It is a further object of the invention to securely adhesively bond the tooth onto the nose piece by an adhesive that fills gaps between the nose piece and the tooth in the tooth pocket. Another object of the invention is to provide a method and tools by which such a secure mounting of teeth can be performed easily and at relatively low cost in the field, with minimal down-time of the excavating equipment. The invention further aims to provide a method and components for refurbishing loose worn teeth on excavating equipment in the field. Another goal of the invention is to reduce or avoid the loosening and loss of teeth from excavating equipment while the teeth are still within their usable service life. Still further, the invention aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as will be apparent from the present specification. The attainment of these objects is, however, not a required limitation of the claimed invention.
The above objects have been achieved according to the invention, wherein an adhesive and preferably a thermosetting epoxy adhesive is disposed in an existing gap between the nose piece and the interior of the tooth pocket during the process of mounting the tooth on the nose piece. The epoxy is allowed to cure, thereby hardening and adhesively bonding the tooth onto the nose piece, in addition to the mechanical connection provided by the tooth fastening arrangement. Preferably, the epoxy substantially fills the existing void volume of the gap or gaps between the nose piece and the tooth pocket, for example filling at least 75% of the void volume, or more preferably at least 90% or even more preferably at least 95% of the void volume. Further preferably, the epoxy is provided in such an amount so that it squeezes out of the opening of the tooth pocket around the shaft or shank of the nose piece, and is smoothed off there to form an epoxy bead or fillet, which seals the gap and prevents the penetration of grit and water. After the epoxy has cured, the epoxy holds the tooth securely and firmly on the nose piece, and prevents wiggling or looseness of the tooth on the nose piece. While most of the digging forces acting on the tooth are transmitted from the tooth directly into the nose piece by direct metal-to-metal contact of the tooth pocket on the nose piece (preferably at least 50% of the nose piece surface area within the tooth pocket is in direct metal-to-metal contact with the tooth), the epoxy also helps to transmit and distribute the loads through additional surface areas that otherwise (without epoxy) would have been open air gaps allowing wiggling looseness of the tooth. Thereby, the epoxy essentially completely stops corrosive, erosive, abrasive and chafing wear of the nose piece and the interior of the tooth pocket during the operating service life of the epoxy.
One method of providing the epoxy involves mixing the two components of the epoxy material to form a viscous activated epoxy liquid or paste, which is poured or injected or applied into the tooth pocket before mounting the tooth on the nose piece. The volume of epoxy to be used must be estimated, so that when the tooth is slid and pressed onto the nose piece, the epoxy will squeeze up and out of the tooth pocket around the shaft or shank of the nose piece, without having excessive overspill of epoxy. A further improved and preferred method involves forming a hole through a solid wall of the tooth, at a location to communicate into the blind bottom of the tooth pocket, e.g. preferably directly at or adjacent to the blind bottom of the tooth pocket, or generally within the gap area between the terminal nose end of the nose piece and the deepest blind bottom of the tooth pocket, or more generally within the deepest 25% or preferably 15%, or 1.5 inches or preferably 1 inch of the depth of the tooth pocket. Then, epoxy is injected, preferably from a two-component epoxy cartridge using a suitable two-component applicator gun, through a mixing tube and a nozzle adapter tip, via the provided epoxy injection hole into the tooth pocket after the tooth has been mounted on the nose piece. The epoxy is thereby injected and flows under pressure into the void space or gap between the nose piece and the interior of the tooth pocket, and flows around and upwardly along the shaft or shank of the nose piece through any existing void channels until the epoxy squeezes out at the opening of the tooth pocket around the nose piece shaft. The epoxy injection hole is preferably located at or sufficiently close to the blind bottom of the tooth pocket so that the injected epoxy will flow into all or substantially all areas (e.g. at the bottom corners) of the gap or void space in the tooth pocket, while filling these areas and flowing upwardly to push out air and not entrap a substantial volume percentage of air bubbles or air pockets. Epoxy is preferably also injected into the fastener hole, before or after installing the fastener arrangement, so that the epoxy also secures the fastener arrangement and seals the fastener hole against penetration of grit and water.
The invention further preferably provides a clamp fixture or holding jig for holding and tightening a tooth in position after the epoxy has been injected, to ensure the tightest possible metal-to-metal contact between the tooth and the nose piece, and to hold the arrangement firmly and securely during the curing of the epoxy.
Further preferably according to the invention, the nose piece and the interior of the tooth pocket are cleaned before mounting the tooth and injecting the epoxy, for example including a degreasing treatment with a suitable solvent to remove any grease, oil, grime, dirt etc., followed by a mechanical abrasive cleaning with a wire brush, needle scaler or sand or grit blasting equipment to clean the surfaces to bare metal and roughen the surfaces for improved adhesive bonding by the epoxy.
In order that the invention may be clearly understood, it will now be explained in further detail in connection with example embodiments thereof, with reference to the accompanying drawings, wherein:
The arrangement as shown in
After the tooth 2 has been mounted on the nose piece 4, i.e. the nose end 4A has been received in the tooth pocket 2A, the tooth is fastened by the fastener arrangement 5. There are many different types of tooth fastener arrangements conventionally available on the market, and the present invention applies to all of such different fastener types. The fastener arrangements typically include a metal fixing pin that mechanically fixes the tooth to the nose piece, and a keeper or retainer that keeps or retains the fixing pin 6 in place. In the simple example illustrated in
To avoid the above described wear and the resulting loss of the tooth or premature maintenance need to replace the tooth, the invention mounts the tooth 2 on the nose piece 4 with an adhesive in addition to the conventional mounting with the fastener arrangement 5. In this regard, the tooth 2 is provided with at least one adhesive injection hole 9 that communicates from the outside of the tooth into the tooth pocket 2A, as will be further discussed next.
As shown in
According to the invention, the void space or gap 10 has been substantially or entirely filled with an adhesive, and preferably a thermosetting, curable, two-component epoxy 11. Methods for achieving this will be described in detail below. Generally, a preferred method involves providing at least one epoxy injection hole 9 through at least one wall of the tooth 2 so as to communicate into the tooth pocket 2A at, adjacent to or near the deepest point in the tooth pocket 2A, i.e. at, adjacent to or near the blind bottom of the tooth pocket 2A. For example, this preferably involves forming the hole 9 at a location so that it communicates into the gap or void space 10 between the terminal end of the nose end 4A of the nose piece 4 and the deepest bottom of the tooth pocket 2A, or preferably within the deepest 25% or 1 inch of the length or depth of the tooth pocket 2A, or most preferably adjoining the very bottom of the tooth pocket 2A. The epoxy 11 is injected under pressure to fill the gap 10 at the furthest bottom of the tooth pocket 2A and also extending upwardly along the sides of the tooth pocket 2A, until the epoxy squeezes out and is preferably smoothed off to form a bead or fillet 12 of epoxy at the opening of the tooth pocket 2A around the body or shank of the nose piece 4. The bead or fillet 12 of epoxy can alternatively or additionally be externally applied in an extra step. Epoxy 11 is preferably additionally injected into the aligned holes 8 to surround the fixing pins 6 and keeper 7 of the tooth fastener arrangement 5, thereby preventing elastic yielding compression of this fastener arrangement and further rigidly holding the tooth 2 on the nose piece 4. The epoxy, preferably filling all voids or gaps 10 around the nose piece 4 in the tooth pocket 2A, serves to securely and fixedly hold the tooth 2 on the nose piece 4 to prevent looseness, wiggling or any other motion of the tooth 2 relative to the nose piece 4. The epoxy also distributes and transmits the forces between the tooth 2 and the nose piece 4, in addition to the areas of direct metal-to-metal contact between the tooth 2 and the nose piece 4. The void-filling epoxy 11, and especially also the bead or fillet 12 of epoxy further serves to prevent or minimize the penetration of grit and/or water into the tooth pocket 2A around the nose piece 4. The above functions together completely prevent or significantly minimize interior wear of the tooth pocket 2A and wear of the nose piece 4 within the tooth pocket 2A, including the above discussed chafing wear, corrosive wear, erosive wear, and abrasive wear. The ultimate effect of the inventive provision of the epoxy adhesive is to prevent or delay the time at which a tooth needs to be replaced due to interior wear or the time at which a tooth falls off and is lost.
Methods of mounting and securing the tooth will now be described in connection with
In a most basic method according to the invention, the indicated steps S1, S2, S3, S5, S7, S8 and S9 can be omitted as unnecessary or not mandatory, and instead of step S5, the epoxy material is simply poured or injected or applied into the tooth pocket of the original unmodified tooth before the tooth is mounted on the nose piece. Such a simple embodiment of the method proceeds as follows. The two components of the epoxy material are measured or dosed and mixed in the appropriate proportions, for example 1:1. The resulting activated epoxy material is then injected, poured or troweled into the tooth pocket of the tooth. The volume of the epoxy material to be applied is estimated based on the volume or size of the gap between the free terminal end of the nose piece and the deepest extent of the tooth pocket as well as additional gap spaces around the sides of the nose piece. An additional amount of epoxy should also be provided to ensure that epoxy will completely fill void spaces and also squeeze out. The excavator bucket is positioned safely in a tooth down orientation, with a bare exposed nose piece. The epoxy-filled tooth pocket is then moved upwardly onto the nose piece in one smooth motion so that the nose piece smoothly submerges into the epoxy and the epoxy squeezes upwardly around the nose piece in the tooth pocket, without creating air bubbles, air pockets or gaps in the epoxy. Once the tooth is fully pushed onto the nose piece, then the fastener arrangement such as a fixing pin and a keeper are installed in the usual manner. The fastener arrangement mechanically holds the tooth tightly on the nose piece until the epoxy cures. Then the excavation equipment may be used in the normal manner.
Further preferred features and steps according to the invention are preferably added to, or substituted in, the above most basic embodiment of the inventive method, as follows. As indicated by steps S1 and S5 in
Step S2 in
If the nose piece is new and unworn, or not significantly worn, then the indicated step S3 is not necessary. On the other hand, if the nose piece 4 is significantly worn, then it is preferred to build-up the worn areas of the nose piece by hard face welding or deposit welding, and then grind the built-up areas to re-shape the nose piece as close as possible to the proper like-new dimensions and configurations, so as to snugly receive the tooth 2 thereon, i.e. to snugly fit into the tooth pocket 2A. This improves the direct metal-to-metal force transmission from the tooth to the nose piece, and enhances the durability of the epoxy.
Next, according to the step 54 as indicated in
The next preferred but optional step is to inject epoxy into the tooth fastener hole 8 in the assembled and aligned tooth 2 and nose piece 4, as indicated by step 55 in
Next, according to the step 57, epoxy is injected through the injection hole 9 into the tooth pocket 2A. This is preferably achieved using a two-component injection gun, such as a caulking gun made for two-component material cartridges. One preferred gun for this purpose is the MixPac™ Type DM 400™ dual cartridge gun. Rather than this manually operated gun, a further preferred electrically operated gun is the Electraflow 400 MR™ from Cox Applicators. Each one of these guns accepts a dual cartridge or two-component dual chamber cartridge of the two components of an epoxy adhesive, and ejects the two components at the appropriate ratio, e.g. 1:1, thereby avoiding operator error in the dispensing or proportioning of the epoxy components. Furthermore, the applicator gun is fitted with a mixing nozzle tube in which the two components are thoroughly mixed as they travel along this nozzle tube before being ejected from the outlet end of the tube. Further according to the invention, the outlet end of the mixing nozzle tube is fitted with a rubber adapter piece for fitting into or sealing against the epoxy injection hole 9 of the tooth 2. For example, a piece of ⅜ inch diameter rubber hose fitted onto the end of the mixing nozzle tube can be pressed against the surface of the tooth 2 to seal tightly around the hole 9 during the epoxy injection process. Preferably, a tapered rubber nozzle fits and seals into the epoxy injection hole and is fitted onto the end of the mixing tube. The gun is then operated to inject mixed epoxy 11 under pressure so that the epoxy flows into the gap or void space 10 and upwardly along the nose piece 4 until epoxy squeezes out at the opening of the tooth pocket 2A. This upward flow of epoxy flushes out air upwardly as the epoxy flows and fills all interconnected voids or gaps. The epoxy squeeze-out is preferably wiped or smoothed to form an epoxy bead or fillet 12 around the body or shank of the nose piece 4 at the junction of the nose piece 4 with the tooth 2 around the tooth pocket 2A.
Rather than merely relying on the fastener arrangement 5 to hold the tooth 2 on the nose piece 4 while the epoxy cures, the invention preferably further provides a special holding clamp arrangement or holding jig 15 as shown in
As shown in
Once the epoxy has cured, the excavation equipment may be placed back into service. As discussed above, the epoxy bond and seal between the tooth and the nose piece eliminates or minimizes internal wear of the tooth and wear of the nose piece. When the exterior of the tooth becomes worn to the end of the service range and the tooth needs to be replaced, it is necessary to break the epoxy bond in order to remove the tooth. This can easily be achieved by heating the tooth with a torch, such as an oxygen/acetylene torch with a rosebud heating tip, to a temperature sufficient until the epoxy fails, for example a temperature of several hundred to 1200° F. As the metal tooth is heated, the metal expands, and tends to expand away from the epoxy bond, and the heating also causes the epoxy to crack, fail and crumble. The tooth can then easily be removed from the nose piece by removing the tooth fastener arrangement and pulling off the tooth. Any remaining epoxy can then be burned, chipped, scraped, sandblasted or otherwise removed from the nose piece. Then a new replacement tooth can be mounted and secured in the above described manner.
Certain tests and test results in the development of the present invention will be described next. Various epoxy formulations were tested for durable steel-to-steel bonding in preliminary experiments. The epoxy-based material that was most-recommended for steel-to-steel bonding by a supplier was Devcon® Plastic Steel® Putty No. 10110, which is a steel-filled epoxy composite material for patching, repairing, rebuilding and bonding all metal surfaces. This epoxy-based material was mixed and prepared according to the label instructions (9:1 mix ratio by weight, 2.5:1 mix ratio by volume), and was used to install a tooth on an Akerman H-10 excavator, following the above inventive procedures without injection of the epoxy material, but rather simply applying the epoxy material into the tooth pocket of the cleaned but otherwise unaltered tooth. After the epoxy fully cured, the excavator was used for normal digging operation for approximately 100 hours of use. At that point, the epoxy-bonded tooth had become as loose as it was previously before the application of epoxy. It is thus regarded that the Devcon® Plastic Steel® Putty No. 10110 material does not achieve an adequate bond and is not sufficiently durable for the inventive application.
Another two-component epoxy formulation was obtained and tested. This epoxy had a 1:1 mix ratio of the two components, and did not include a steel filler. This epoxy was used to install and secure all eight teeth on a John Deere 544 bucket loader. After normal loading use of 45 hours on the John Deere 544 loader, all of the teeth remained tight and secure, i.e. no teeth showed any looseness or movement. After another seven weeks of essentially full time use on the John Deere 544 loader, all of the teeth still remained tight and secure with no movement. After 500 hours of use of the John Deere 544 loader, two of the teeth showed some loose movement, while the other six teeth remained tight and secure with no movement. All of the teeth have remained attached to the nose pieces on the bucket, i.e. no teeth have fallen off.
This epoxy material was also used to install all five teeth of a Caterpillar 330 excavator. After about seven weeks of essentially full time use of the Caterpillar 330 excavator, one tooth showed some looseness and movement, while the four other teeth remained tight and secure with no movement. After approximately 800 hours of normal digging operation with the Caterpillar 330 excavator, three of the teeth showed some looseness and movement while two of the teeth still remained tight and secure with no movement. All of the teeth have remained attached to the nose pieces on the bucket, i.e. no teeth have fallen off.
The above epoxy formulation was also used to attach and secure all seven teeth of the Akerman H-10 excavator. After 500 hours of normal digging operation, all of the teeth remained tight and secure with no movement. After approximately 600 hours of normal digging operation, two of the teeth began to slightly loosen and show movement, while five of the teeth remained completely tight and secure with no movement. After 900 hours of digging use, one tooth remained completely tight and secure with no movement, and six teeth showed some slight movement, but all teeth remained attached, i.e. no teeth had fallen off. Upon removing the six loose teeth and inspecting the tooth pockets and the nose pieces, it was subjectively evaluated or judged, based on the inventor's 35 years of experience in the excavation field, that the tooth pockets and nose pieces show significantly less wear than would ordinarily be the case after 900 hours of use with a conventional mounting method (mechanical fastening) without the inventive use of epoxy.
The inventor requested changes to the above epoxy formulation so as to increase the viscosity for making the application process easier, and to increase the bond strength and inherent material strength of the cured epoxy. The viscosity should be high (thick) enough so that the injected epoxy will stay in place in the pocket and the fastener hole, and will not ooze back out through the injection hole or the fastener hole. On the other hand, the viscosity should be low (thin) enough so that the injected epoxy readily flows into and throughout substantially all void spaces of the tooth pocket under the injection pressure from the manual adhesive injection gun, and will not create too high of a back pressure in the gun which could cause the epoxy components to squeeze past the plungers of the epoxy component cartridges back out of the rear of the gun.
The resultant revised epoxy formulation based on the inventor's requested modifications is now commercially available as AAS Steelbond™ structural adhesive from Advanced Adhesive Systems, 681 North Mountain Road, Newington, Conn. 06111, USA. This epoxy is a 1:1 proportioned, thermosetting, two-component epoxy formulated to have an uncured viscosity of 250,000 for part A and 220,000 for part B (cps, spindle test TE, 2.5 rpm), an uncured density of 8.07 for part A and 8.05 for part B (lbs./gallon), an off-white color for part A, an amber color for part B, and a flash point of 51° F. (LCC). The mixed viscosity is 255,000 cps and the mixed density is 8.05 lbs./gallon. The formulation provides a 10 to 15 minute mixer tube life, a total working time of 15 to 20 minutes, a maximum fixture time of 30 to 35 minutes and a typical fixture time on all surfaces in 20 to 25 minutes or less. The bonds will develop 80% cure in two hours, and 100% cure in four hours. The cured material in a steel-to-steel bond provides a high tensile strength of at least 3,500 psi or optimally greater than 3,800 psi in a tensile sheer test according to ASTM D1002, on metal surfaces in as-received condition with no surface preparation. The cured epoxy on sandblasted steel strips provides a good peel strength of greater than 40 pli. The epoxy also provides a good impact strength on steel-to-steel bonds, of greater than 6.0 joules/in2 according to a GMC
Auto Side Impact Test. This adhesive is available in two-component 400 ml cartridges, for use in the abovementioned preferred two-component applicator guns, and is also available in 5 gallon pails and 50 gallon drums. This AAS Steelbond™ epoxy adhesive has been improved over the previously tested epoxy mentioned above, and is considered to be the most preferred adhesive for the present inventive application, although it is considered that other epoxy materials of thermosetting two-component type without steel filler or without other fillers, and preferably of 1:1 mix ratio, are also suitable and serviceable according to the invention, for example the abovementioned epoxy before the improving modifications were made.
While the epoxy is suitable for bonding on “as-received” new steel forged parts or machined surfaces, it is further considered that better bonding will be achieved on excavation equipment tooth pockets and nose pieces (both new and used) by first cleaning those surfaces as described above, namely to remove any loose surface dirt, then by degreasing with a solvent to remove any grease or oil, and then by abrasive cleaning with a sandblasting gun or with a needle scaler or wire brush to provide a clean, bare metal surface with a roughened texture and without any paint, rust, scale or other contaminant residue. The above described tests were conducted without such cleaning procedures beyond removing dirt. The newest improved and preferred procedure using these cleaning steps and using the improved preferred AAS Steelbond™ epoxy material was carried out when removing and reinstalling the six loose teeth of the Akerman H-10 excavator discussed above. Namely, these teeth and the associated nose pieces were cleaned using sandblasting, and were then reinstalled using the new improved epoxy material. These six teeth remain tight and secure, and the seventh tooth that had been installed using the previous epoxy formulation without sandblasting also still remains tight and secure, at the time of filing the present application.
The above tests were carried out on severely worn, used teeth and nose pieces, and demonstrated that the inventive method and combination can be used to refurbish or retrofit existing used or worn excavation equipment with only cleaning steps as described (and without needing to use new teeth and without requiring the nose pieces to be re-built with hard face welding and grinding). A further test was conducted on a Caterpillar 315 excavator having severely worn, used teeth and nose pieces. The nose pieces were first cleaned as described above. Then the worn surfaces were built up with hard face welding, and the added weld metal was ground with a grinder to re-shape the surface to near-new specifications (shape and dimensions). New teeth were then cleaned (in the tooth pockets thereof) and provided with epoxy injection holes as described above, and mounted on the re-built nose pieces with new pins and keepers. The preferred formulation epoxy was injected as described above to secure the teeth, and the teeth were tightened and held in place with the holding clamp arrangement, while the epoxy cured. Then the excavator was put back into service. All of the teeth remain tight and secure at the time of filing the present patent application. While insufficient digging time has elapsed to validate this, it is expected that the best results will be obtained in such an installation starting with new teeth rather than worn teeth, and with re-built nose pieces (or preferably new nose pieces) because the most direct metal-to-metal contact of the nose piece in the tooth pocket is achieved and the epoxy merely needs to provide supplemental support, strengthening and sealing rather than providing a substantial portion of the force transmission between the tooth and the nose piece. Another intermediate option would be to build up the worn nose pieces with excess weld metal and grind the nose pieces to a larger-than-new size and shape to fit the worn interior pockets of the used teeth rather than replacing the worn teeth with new teeth. The object is to achieve the best reasonably possible metal-to-metal fit inside the tooth pockets before injecting the epoxy.
Furthermore, a test was conducted to try to allow easier removal of a tooth on which the epoxy was still intact, without requiring torch-heating of the tooth to break the epoxy. In this regard, a plastic bag was placed into the tooth pocket as a liner and the epoxy was placed into the bag. Then, the tooth was pushed onto the nose piece in the normal manner, so that the epoxy surrounded and bonded onto the nose piece and squeezed-out at the top of the opening of the tooth pocket. The plastic bag, however, isolated the epoxy from the tooth, so that the epoxy did not bond to the interior surfaces of the tooth pock et. The epoxy was cured and the tooth was put into operation in the normal manner. This test failed after a short time of digging, in that the tooth became loose, despite the epoxy filling the voids between the nose piece and the tooth pocket. From this test, it is considered important that the epoxy shall bond onto the nose piece and the interior surfaces of the tooth pocket, so as to bond the two components to one another. The epoxy does not merely serve a void-filling function, but also a bonding function. This surface bond onto the tooth and the nose piece also prevents water and grit from corrosively or abrasively wearing surfaces that would otherwise be exposed. This test also emphasized that steps should preferably be taken to enhance the bond of the epoxy onto the metal surfaces of both the tooth pocket and the nose piece, for example with the cleaning, degreasing and sandblasting steps described above, before introducing the epoxy.
The above tests and test results have shown that the inventive application of an adhesive and preferably a thermosetting two-component epoxy, and most preferably the specific preferred epoxy mentioned above, for mounting and securing replaceable ground-engaging wear points on nose pieces of excavation equipment, extends the useful operating life of the replaceable wear points, because it prevents or reduces looseness and the resulting interior wear of the teeth and the nose pieces on which they are mounted. It thus ultimately prevents or delays the time at which a tooth must be replaced because it has become too loose or because it has fallen off. Inspection of the tooth pockets and nose pieces after conducting the tests has also shown that these surfaces exhibit significantly less wear than would ordinarily be the case if no epoxy had been used according to the inventive method but instead the teeth had been mounted conventionally. The above tests have also shown that the loss of teeth due to teeth falling off can be prevented or delayed through the use of the inventive epoxy-mounting of the teeth.
The inventive application of an adhesive and preferably epoxy into the existing gap or void space in the tooth pocket between the tooth and the nose piece is achieved with simple procedures that can easily be carried out in the field, with relatively inexpensive materials and tools, and has been shown to achieve a durable result in normal field use. With the inventive epoxy-mounting arrangement, it is not necessary to provide a metal weld of the tooth onto the nose piece, and it is not necessary to provide a dirt shield collar or an o-ring seal to try to keep dirt and water out of the tooth pocket on the nose piece. Thus, the inventive arrangement and method preferably expressly exclude such a weld joint, such a dirt shield collar, and such an o-ring seal.
Although the invention has been described with reference to specific example embodiments, it will be appreciated that it is intended to cover all modifications and equivalents within the scope of the appended claims. It should also be understood that the present disclosure includes all possible combinations of any individual features recited in any of the appended claims. The abstract of the disclosure does not define or limit the claimed invention, but rather merely abstracts certain features disclosed in the application.
