CA1211136A - Wheel ditcher tooth - Google Patents
Wheel ditcher toothInfo
- Publication number
- CA1211136A CA1211136A CA000443237A CA443237A CA1211136A CA 1211136 A CA1211136 A CA 1211136A CA 000443237 A CA000443237 A CA 000443237A CA 443237 A CA443237 A CA 443237A CA 1211136 A CA1211136 A CA 1211136A
- Authority
- CA
- Canada
- Prior art keywords
- tooth
- teeth
- wheel
- bucket
- elongated members
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/28—Small metalwork for digging elements, e.g. teeth scraper bits
- E02F9/2808—Teeth
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/28—Small metalwork for digging elements, e.g. teeth scraper bits
- E02F9/2866—Small metalwork for digging elements, e.g. teeth scraper bits for rotating digging elements
Landscapes
- Engineering & Computer Science (AREA)
- Mining & Mineral Resources (AREA)
- Civil Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Structural Engineering (AREA)
- Component Parts Of Construction Machinery (AREA)
Abstract
ABSTRACT
The invention is a tooth mountable on a bucket of the digging wheel of a wheel-type ditching machine. The tooth has its ends angularly offset from each other, and the digging end has a generally U-shaped cross-section formed by a central section and a pair of integral outer flange sections. A series of elongated members of high wear resistance extend through the central section and are adapted to impact with the ground during the digging operation. The tooth of the invention has shown greater resistance to wear than previously-known types of teeth when used in permafrost conditions.
The invention is a tooth mountable on a bucket of the digging wheel of a wheel-type ditching machine. The tooth has its ends angularly offset from each other, and the digging end has a generally U-shaped cross-section formed by a central section and a pair of integral outer flange sections. A series of elongated members of high wear resistance extend through the central section and are adapted to impact with the ground during the digging operation. The tooth of the invention has shown greater resistance to wear than previously-known types of teeth when used in permafrost conditions.
Description
WHEEL DITHER TOOTH
This invention relates to a replaceable tooth for a wheel-type ditching machine, and more particularly, to that type of tooth having wear-resistant elongated members extending there-through.
A wheel-type ditching machine is a traction-type vehicle on which is mounted a rotatable, elevatable digging wheel having a series of buckets attached to its periphery, each bucket having secured to it a number of detachable digging teeth. The teeth are attached to the buckets so as to extend forward of the open end and make the initial contact with the ground. Various types of dither teeth are utilized, and an important con-side ration in choosing the construction of a ditch tooth is the type of material being excavated. For ditching operations in cold climates, an especially strong and durable tooth is required. If the tooth it not sufficiently strong and durable it will either fracture or else wear at an unacceptably fast rate.
With the increasing number of oil and gas pipelines being installed in territory where permafrost exists, wheel ditching teeth produced for ditching operations in warmer climates have proven unacceptable. This is true of those types of teeth formed from steel alone, as well as those steel teeth which have hardened elongated members extending there through. As mentioned, such teeth either fracture or wear too rapidly when utilized in cold regions with a deep frost level.
The subject invention is a tooth adapted to be mounted on a bucket of a digging wheel of a wheel-type ditching Lo machine, which tooth has both good wear-resistance and high strength, and is inexpensive to manufacture. The tooth has a first end and a second end, the first end being angularly offset from the second end. The first end has means for 5 connecting the tooth to the bucket, and the second end which is adapted to make contact with the ground, has a generally U-shaped cross-section. The U-shaped cross-section comprises a central section and a pair of integral outer flange sections positioned generally perpendicular thereto, the central 10 section extending generally perpendicular to the angle of offset. The flange sections connect integrally with the first end to provide structural rigidity to the central section of the second end. A series of elongated members extend longitudinally through the central section of the 15 second end and those members are formed from a material having greater wear-resistance than the material of the no-maunder of the tooth.
The first end may be configured as a female coupling adapted for complementary engagement with a male coupling 20 connected to the bucket so as to extend forward thereof. The tooth may be adapted to be mounted on the bucket such that, when mounted, each of the series of elongated members on the tooth is oriented to extend at approximately 25 relative to a line extending between the center of the wheel and the tooth.
25 The tooth may be one of a series of identical teeth adapted to be mounted on the buckets of the wheel such that in one direction around the wheel every third bucket has the teeth mountable thereon in the same configuration, and each of the teeth of each third bucket is laterally offset from each of 30 the teeth on the intervening pair of buckets. The series of elongated members may comprise four cylindrical pins in planar alignment, the pins extending in parallel spaced relation longitudinally through the central section of the second end.
Each pin may be formed from a composition of approx-35 irately 84% tungsten carbide by weight and 16% cobalt by weight. The remainder of the tooth may be formed from an iron alloy composition having a nickel content by weight approximately between 2.5% and 3.25~. The iron alloy composition may also have a carbon content by weight approx-irately between 0.16% and 0.22%. Also, the iron alloy composition may have a manganese content by weight approx-irately between 0.6% and 1.0%. The iron alloy composition may contain carbon, manganese, silicon, nickel, chronimum and molyledeum.
In another form the invention comprises the process for manufacturing the teeth of the subject invention. That process comprises the steps of, firstly, positioning a series of extended elongated members, each approximately twice the length of the elongated members in finished teeth, such that those extended elongated members extend into an adjacent pair of cavities for forming two teeth. One end of each extended elongated member extends into one cavity and the other end of each such member extends into the other cavity. The process comprises the second step of casting the teeth with the extended elongated members in the position assumed in the first step such that, after casting, the teeth are connected only by the extended elongated members extending there between. The third step of the process is dividing each extended elongated member into two parts generally centrally of its length, after the casting, such that one portion of each extended elongated member extends from one tooth and the other portion extends from the other tooth.
The extended elongated members utilized in the process may have a circumferential groove formed at approximately the mid-point of its length, the groove defining a region of weakness and facilitating the defining of each extended elongated member into two parts. The series of elongated members may comprise four cylindrical pins in planar alignment, the pins extending in parallel spaced relation through one end of the tooth. Also, each outer end of each extended elongated member may be generally conical-shaped.
The subject invention will now be more fully described by means of a preferred embodiment utilizing the accompanying lo drawings, in which:
Figure 1 is a side view of a wheel-type ditching machine.
Figure 2 is a plan view of the tooth of the subject invention.
Figure 3 is a cross-sectional end view through section 3-3 of the tooth of the subject invention.
Figure 4 is a side view of the tooth of the subject invention.
Figure 5 is a perspective view of the tooth of the subject invention.
Figure 6 is a side view of a portion of a digging wheel of a ditching machine, a bucket on that wheel, and a tooth of the subject invention on that bucket.
Figure 7 is a perspective view of three successively-positioned buckets on a ditching wheel, each of the buckets having the teeth of the subject invention secured thereto in offset lateral positions.
Figure 8 is a partially-sectioned side view of a ditch being created by the advancing, rotating digging wheel of a dither machine.
Figure 9 is a schematic view of the relative teeth positions on five successively-positioned buckets on a digging wheel, the view illustrating the digging pattern created by the teeth.
Figure 10 is a perspective view of a mound having an adjacent pair of cavities for simultaneously forming two teeth of the subject invention.
Figure 11 is a perspective view of one of the extended elongated members shown centrally positioned in Figure 10.
The dither teeth of the subject invention were utilized with a Banister Model 710 wheel excavator equipped with an excavating wheel employing Esco Corporation-manufactured buckets and tooth adaptation system. Figure 1 generally illustrates in side view a wheel-ditching machine similar to 35 the Banister Model 710. Full scale tests were undertaken with this machine and two early types of dither teeth at 7 sites in the vicinity of Roe Point on Melville Island. The J
1~111.;~
Banister Model 710 excavator proved that it is well suited for ditching in the High Arctic. Unfortunately, the teeth tested were less suitable in that they wrote rapidly when the excavator was operated at acceptable ditching rates, the resultant tooth S replacement cost being unacceptably high.
Upon analysis of the Melville Island terrain, it became evident that that terrain has virtually no hard, impact-producing rock and boulders within the first few meters below the ground surface. Also, it was evident that the soil is extremely abrasive. Further, due to low year-round temperatures, the ground is in a permanent frozen state and the terrain presents a considerably greater resistance to excavation than if it were only seasonally frozen. All of these factors led to the tested types of dither teeth having a very limited life and also a defined point where that life expired. The visible result of the termination of teeth utility was the walking or climbing up of the digging wheel on the ditch face. In other words, the useful life of the teeth expires when the soil's resistance exceeds the pressure applied by the teeth at the bottom of the ditch. The pressure at this point results mainly from the wheel weight, that weight as a vertical force divided by the total area of the teeth pushed into the ditch being the pressure.
So long as that tooth pressure exceeds the soil's resistive force, excavation occurs if adequate torque is applied to the wheel. The field tests demonstrated that both the horizontal force applied on the wheel against the ditch face, and the wheel torque were adequate.
Effective wheel weight and the area of the portion of the teeth in contact with the ditch face were then examined.
Since the Banister Model 710 wheel excavator has a set, tested configuration and a known effective wheel weight, the only factor to which improvement could be made was the wear area of the teeth.
or non-abrasive soils with high ice content, steel dither teeth without elongated inserts are adequate provided that the teeth are sufficiently strong and a minimum cross-sectional wear area can be maintained. However, such teeth can barely penetrate abrasive terrain and teeth formed exclusively of steel wear unacceptably fast in such terrain.
The addition of elongated members, such as carbide pins, to teeth enhances both the penetration capability and the wear-resistance of such teeth in an abrasive terrain. Extensive testing resulted in a determination that the tooth illustrated in Figures 2, 3, 4 and 5 presented the best combination of strength and low wear-resistance in the abrasive terrain of the High Arctic. With reference to those four Figures, the tooth which is generally designated 20 has one end adapted to connect with one of the buckets 21 on digging wheel 22 of ditching machine 23. That first end of tooth 20 is generally shaped as a pocket having a shell portion 24 surrounding a cavity 25 of inwardly-decreasing cross-section. A corresponding projection 27 shown in Figure 7) on each bucket 21 has a configuration complementary to cavity 25. A fastening pin 28 extends through a hole (not shown) in each projection 27 and the pair of holes 29 on each tooth Jo maintain that tooth in position.
As shown in Figure 2, the other end of each tooth 20 is narrower in plan view, and Figure 4 illustrates that the two ends of tooth 20 are angularly offset from each other. That angular offset, which was not present in the teeth utilized in the previous testing, has a purpose which will subsequently become more clear. The second end of tooth 20 has 4 tungsten carbide pins 30 extending in a longitudinal direction there-through. The pins 30 contain by weight 84% tungsten carbide and 16% cobalt. Each pin 30 shown in Figure 2 is approx-irately 75 millimeters long and 10 millimeters in diameter The pins are in planar spaced relation, and separated by a distance of 4 millimeters. The distance of each of the outer pins 30 from the respective side of tooth 20 is 5 millimeters, and the total width of the second end of tooth 20 is 62 millimeters. The central portion of the second end of tooth 20 is 18 mlllimetres deep, as shown in Figure 3.
Additionally, an integral flange section of depth 18 , sly millimeters extends lengthwise along the second end of tooth 20, as shown in Figures 3 and 4, the purpose of the flange sections is to provide increased rigidity and strength to tooth 20. As shown in Figure 4, the flange sections have a rounded contour where they meet the outer face of the second end of tooth I The carbide pins 30 are each one half of a 150 millimetre-long pin 31 (as shown in Figure if) which is manufactured with a circumferential groove 33 at its long-itudinal mid-point. The pins 31 are manufactured by Teledyne Fifth Sterling of Houston, Texas with its Grade H71 carbide material; as mentioned, that carbide material is 84% by weight tungsten carbide and 16% by weight cobalt.
s shown in Figure 6, when mounted on a bucket 21, the second end of each tooth is oriented at an angle of approx-irately 25~ relative to a line extending radially on digging wheel 22 through that tooth. The 25 angle is referred to as the rake angle. Teeth utilized in the early experiments had a rake angle of approximately 45; they did not have any offset angle between their ends, and their longitudinal axis extended in-line with projection 27 on bucket 21. It was found that with teeth having no offset angle the wear on the digging end of the tooth was at an angle relative to the longitudinal axis;
a weak tooth with a high wear area resulted. The rake angle of the teeth of the subject invention was therefore chosen to be 25 rather than 45.
The teeth were manufactured in pairs utilizing the mound 35 shown in Figure 10. During each casting, four 150 millimeter-long carbide pins 31 were positioned to extend through a core piece 36 having a thickness of 15 millimeters, the circumfer-entail grooves of the pins 31 being centered within corpus 36. The mound 35 as shown in Figure 10 is only the bottom portion, and a corresponding upper portion having a pour hole is also utilized. The pour hole of the upper portion of the mound would extend generally above the region 37 of mound 35, and molten steel entering the region 37 would in turn flow into the regions 38 and 39. After solidifying, the pair of cast teeth are removed together from the mound and machined to remove any excess casting material. Foothill Steel Foundry of Calgary cast the teeth from ON Alloy, which is an iron alloy with the following additives:
Additives % By Weight carbon 0.16-0.22 manganese 0.60-1.00 silicon 0.60 (maximum) nickel 2.50-3.25 chromium 0-50-0 90 10 molybdenum 0. 20-0. 40 The production of ON alloy involves its heat-treatment for adequate strength and wear-reslstance. The teeth are heat treated by austenitizing them at 1700F for 105 hours, then oil quenching them, then tempering them. As can be seen in the drawings, both ends of each of the pins 31 are generally conical-shaped; the reason for that shape is to minimize the stress at the interface between each carbide pin 30 and the cast portion of tooth 20.
The stress may be further minimized by staggering the ends of the pins at the interface. After the pair of teeth are 20 removed from the mound, a bending force is applied to separate the teeth by fracturing the four pins 31 at circumferential groove 33. Each pin 31 then becomes a pair of pins 30 each extending approximately 7.5 millimeters out of the one end of tooth 20.
When in use, the wear-resistance of the steel body of the tooth is low compared to that of the tungsten carbide pins. The exposed steel abrades faster than does the exposed carbide 9 resulting in the pins protruding further and further out of the body of the tooth. Some of the pins will break 30 off when the shear force becomes too great. However, as the wear continues, the broken pins begin to again protrude from the body of the tooth. A more wear-resistant alloy for the body of the tooth would not change this self-compensating mode of wear, but only slow down the process. On the other 35 hand, the spacing between pins controls the rate of wear g between them. It is the combination of the material utilized in the body of the tooth, and the size and relative spacing of the carbide pins which determines the tooth wear rate, i.e.
the tooth's ability to penetrate without excessive stressing of protruding carbide pins. The choice of the material for the body of the tooth and the carbide pins determines the strength and overall wear-resistance of the teeth; however, pin spacing governs the ability of the teeth to penetrate the face of the ditch. In effect, a pair of counteracting considerations are present. If the spacing of the pins is too close then penetration of the ditch face will be hampered due to inadequate pin protrusion. Harder soils require greater penetration of the teeth and thus wider spacing between the carbide pins, but such wider spacing generates greater wear on the body of the teeth and thus tends to result in greater breakage of the pins. The foregoing considerations and casting practicalities dictated the final positioning of the four pins in the teeth. As earlier discussed, each pin 30 is approx-irately 75 millimeters long and, of that length, approximately 7 to 8 millimeters protrudes from the body of the tooth. The maximum theoretical wear length is 60 to 65 molters. If the tooth is positioned on the bucket such that the rake angle is 25, as earlier discussed, then the area of the wear surface of the tooth remains almost constant over its entire usable length.
This invention relates to a replaceable tooth for a wheel-type ditching machine, and more particularly, to that type of tooth having wear-resistant elongated members extending there-through.
A wheel-type ditching machine is a traction-type vehicle on which is mounted a rotatable, elevatable digging wheel having a series of buckets attached to its periphery, each bucket having secured to it a number of detachable digging teeth. The teeth are attached to the buckets so as to extend forward of the open end and make the initial contact with the ground. Various types of dither teeth are utilized, and an important con-side ration in choosing the construction of a ditch tooth is the type of material being excavated. For ditching operations in cold climates, an especially strong and durable tooth is required. If the tooth it not sufficiently strong and durable it will either fracture or else wear at an unacceptably fast rate.
With the increasing number of oil and gas pipelines being installed in territory where permafrost exists, wheel ditching teeth produced for ditching operations in warmer climates have proven unacceptable. This is true of those types of teeth formed from steel alone, as well as those steel teeth which have hardened elongated members extending there through. As mentioned, such teeth either fracture or wear too rapidly when utilized in cold regions with a deep frost level.
The subject invention is a tooth adapted to be mounted on a bucket of a digging wheel of a wheel-type ditching Lo machine, which tooth has both good wear-resistance and high strength, and is inexpensive to manufacture. The tooth has a first end and a second end, the first end being angularly offset from the second end. The first end has means for 5 connecting the tooth to the bucket, and the second end which is adapted to make contact with the ground, has a generally U-shaped cross-section. The U-shaped cross-section comprises a central section and a pair of integral outer flange sections positioned generally perpendicular thereto, the central 10 section extending generally perpendicular to the angle of offset. The flange sections connect integrally with the first end to provide structural rigidity to the central section of the second end. A series of elongated members extend longitudinally through the central section of the 15 second end and those members are formed from a material having greater wear-resistance than the material of the no-maunder of the tooth.
The first end may be configured as a female coupling adapted for complementary engagement with a male coupling 20 connected to the bucket so as to extend forward thereof. The tooth may be adapted to be mounted on the bucket such that, when mounted, each of the series of elongated members on the tooth is oriented to extend at approximately 25 relative to a line extending between the center of the wheel and the tooth.
25 The tooth may be one of a series of identical teeth adapted to be mounted on the buckets of the wheel such that in one direction around the wheel every third bucket has the teeth mountable thereon in the same configuration, and each of the teeth of each third bucket is laterally offset from each of 30 the teeth on the intervening pair of buckets. The series of elongated members may comprise four cylindrical pins in planar alignment, the pins extending in parallel spaced relation longitudinally through the central section of the second end.
Each pin may be formed from a composition of approx-35 irately 84% tungsten carbide by weight and 16% cobalt by weight. The remainder of the tooth may be formed from an iron alloy composition having a nickel content by weight approximately between 2.5% and 3.25~. The iron alloy composition may also have a carbon content by weight approx-irately between 0.16% and 0.22%. Also, the iron alloy composition may have a manganese content by weight approx-irately between 0.6% and 1.0%. The iron alloy composition may contain carbon, manganese, silicon, nickel, chronimum and molyledeum.
In another form the invention comprises the process for manufacturing the teeth of the subject invention. That process comprises the steps of, firstly, positioning a series of extended elongated members, each approximately twice the length of the elongated members in finished teeth, such that those extended elongated members extend into an adjacent pair of cavities for forming two teeth. One end of each extended elongated member extends into one cavity and the other end of each such member extends into the other cavity. The process comprises the second step of casting the teeth with the extended elongated members in the position assumed in the first step such that, after casting, the teeth are connected only by the extended elongated members extending there between. The third step of the process is dividing each extended elongated member into two parts generally centrally of its length, after the casting, such that one portion of each extended elongated member extends from one tooth and the other portion extends from the other tooth.
The extended elongated members utilized in the process may have a circumferential groove formed at approximately the mid-point of its length, the groove defining a region of weakness and facilitating the defining of each extended elongated member into two parts. The series of elongated members may comprise four cylindrical pins in planar alignment, the pins extending in parallel spaced relation through one end of the tooth. Also, each outer end of each extended elongated member may be generally conical-shaped.
The subject invention will now be more fully described by means of a preferred embodiment utilizing the accompanying lo drawings, in which:
Figure 1 is a side view of a wheel-type ditching machine.
Figure 2 is a plan view of the tooth of the subject invention.
Figure 3 is a cross-sectional end view through section 3-3 of the tooth of the subject invention.
Figure 4 is a side view of the tooth of the subject invention.
Figure 5 is a perspective view of the tooth of the subject invention.
Figure 6 is a side view of a portion of a digging wheel of a ditching machine, a bucket on that wheel, and a tooth of the subject invention on that bucket.
Figure 7 is a perspective view of three successively-positioned buckets on a ditching wheel, each of the buckets having the teeth of the subject invention secured thereto in offset lateral positions.
Figure 8 is a partially-sectioned side view of a ditch being created by the advancing, rotating digging wheel of a dither machine.
Figure 9 is a schematic view of the relative teeth positions on five successively-positioned buckets on a digging wheel, the view illustrating the digging pattern created by the teeth.
Figure 10 is a perspective view of a mound having an adjacent pair of cavities for simultaneously forming two teeth of the subject invention.
Figure 11 is a perspective view of one of the extended elongated members shown centrally positioned in Figure 10.
The dither teeth of the subject invention were utilized with a Banister Model 710 wheel excavator equipped with an excavating wheel employing Esco Corporation-manufactured buckets and tooth adaptation system. Figure 1 generally illustrates in side view a wheel-ditching machine similar to 35 the Banister Model 710. Full scale tests were undertaken with this machine and two early types of dither teeth at 7 sites in the vicinity of Roe Point on Melville Island. The J
1~111.;~
Banister Model 710 excavator proved that it is well suited for ditching in the High Arctic. Unfortunately, the teeth tested were less suitable in that they wrote rapidly when the excavator was operated at acceptable ditching rates, the resultant tooth S replacement cost being unacceptably high.
Upon analysis of the Melville Island terrain, it became evident that that terrain has virtually no hard, impact-producing rock and boulders within the first few meters below the ground surface. Also, it was evident that the soil is extremely abrasive. Further, due to low year-round temperatures, the ground is in a permanent frozen state and the terrain presents a considerably greater resistance to excavation than if it were only seasonally frozen. All of these factors led to the tested types of dither teeth having a very limited life and also a defined point where that life expired. The visible result of the termination of teeth utility was the walking or climbing up of the digging wheel on the ditch face. In other words, the useful life of the teeth expires when the soil's resistance exceeds the pressure applied by the teeth at the bottom of the ditch. The pressure at this point results mainly from the wheel weight, that weight as a vertical force divided by the total area of the teeth pushed into the ditch being the pressure.
So long as that tooth pressure exceeds the soil's resistive force, excavation occurs if adequate torque is applied to the wheel. The field tests demonstrated that both the horizontal force applied on the wheel against the ditch face, and the wheel torque were adequate.
Effective wheel weight and the area of the portion of the teeth in contact with the ditch face were then examined.
Since the Banister Model 710 wheel excavator has a set, tested configuration and a known effective wheel weight, the only factor to which improvement could be made was the wear area of the teeth.
or non-abrasive soils with high ice content, steel dither teeth without elongated inserts are adequate provided that the teeth are sufficiently strong and a minimum cross-sectional wear area can be maintained. However, such teeth can barely penetrate abrasive terrain and teeth formed exclusively of steel wear unacceptably fast in such terrain.
The addition of elongated members, such as carbide pins, to teeth enhances both the penetration capability and the wear-resistance of such teeth in an abrasive terrain. Extensive testing resulted in a determination that the tooth illustrated in Figures 2, 3, 4 and 5 presented the best combination of strength and low wear-resistance in the abrasive terrain of the High Arctic. With reference to those four Figures, the tooth which is generally designated 20 has one end adapted to connect with one of the buckets 21 on digging wheel 22 of ditching machine 23. That first end of tooth 20 is generally shaped as a pocket having a shell portion 24 surrounding a cavity 25 of inwardly-decreasing cross-section. A corresponding projection 27 shown in Figure 7) on each bucket 21 has a configuration complementary to cavity 25. A fastening pin 28 extends through a hole (not shown) in each projection 27 and the pair of holes 29 on each tooth Jo maintain that tooth in position.
As shown in Figure 2, the other end of each tooth 20 is narrower in plan view, and Figure 4 illustrates that the two ends of tooth 20 are angularly offset from each other. That angular offset, which was not present in the teeth utilized in the previous testing, has a purpose which will subsequently become more clear. The second end of tooth 20 has 4 tungsten carbide pins 30 extending in a longitudinal direction there-through. The pins 30 contain by weight 84% tungsten carbide and 16% cobalt. Each pin 30 shown in Figure 2 is approx-irately 75 millimeters long and 10 millimeters in diameter The pins are in planar spaced relation, and separated by a distance of 4 millimeters. The distance of each of the outer pins 30 from the respective side of tooth 20 is 5 millimeters, and the total width of the second end of tooth 20 is 62 millimeters. The central portion of the second end of tooth 20 is 18 mlllimetres deep, as shown in Figure 3.
Additionally, an integral flange section of depth 18 , sly millimeters extends lengthwise along the second end of tooth 20, as shown in Figures 3 and 4, the purpose of the flange sections is to provide increased rigidity and strength to tooth 20. As shown in Figure 4, the flange sections have a rounded contour where they meet the outer face of the second end of tooth I The carbide pins 30 are each one half of a 150 millimetre-long pin 31 (as shown in Figure if) which is manufactured with a circumferential groove 33 at its long-itudinal mid-point. The pins 31 are manufactured by Teledyne Fifth Sterling of Houston, Texas with its Grade H71 carbide material; as mentioned, that carbide material is 84% by weight tungsten carbide and 16% by weight cobalt.
s shown in Figure 6, when mounted on a bucket 21, the second end of each tooth is oriented at an angle of approx-irately 25~ relative to a line extending radially on digging wheel 22 through that tooth. The 25 angle is referred to as the rake angle. Teeth utilized in the early experiments had a rake angle of approximately 45; they did not have any offset angle between their ends, and their longitudinal axis extended in-line with projection 27 on bucket 21. It was found that with teeth having no offset angle the wear on the digging end of the tooth was at an angle relative to the longitudinal axis;
a weak tooth with a high wear area resulted. The rake angle of the teeth of the subject invention was therefore chosen to be 25 rather than 45.
The teeth were manufactured in pairs utilizing the mound 35 shown in Figure 10. During each casting, four 150 millimeter-long carbide pins 31 were positioned to extend through a core piece 36 having a thickness of 15 millimeters, the circumfer-entail grooves of the pins 31 being centered within corpus 36. The mound 35 as shown in Figure 10 is only the bottom portion, and a corresponding upper portion having a pour hole is also utilized. The pour hole of the upper portion of the mound would extend generally above the region 37 of mound 35, and molten steel entering the region 37 would in turn flow into the regions 38 and 39. After solidifying, the pair of cast teeth are removed together from the mound and machined to remove any excess casting material. Foothill Steel Foundry of Calgary cast the teeth from ON Alloy, which is an iron alloy with the following additives:
Additives % By Weight carbon 0.16-0.22 manganese 0.60-1.00 silicon 0.60 (maximum) nickel 2.50-3.25 chromium 0-50-0 90 10 molybdenum 0. 20-0. 40 The production of ON alloy involves its heat-treatment for adequate strength and wear-reslstance. The teeth are heat treated by austenitizing them at 1700F for 105 hours, then oil quenching them, then tempering them. As can be seen in the drawings, both ends of each of the pins 31 are generally conical-shaped; the reason for that shape is to minimize the stress at the interface between each carbide pin 30 and the cast portion of tooth 20.
The stress may be further minimized by staggering the ends of the pins at the interface. After the pair of teeth are 20 removed from the mound, a bending force is applied to separate the teeth by fracturing the four pins 31 at circumferential groove 33. Each pin 31 then becomes a pair of pins 30 each extending approximately 7.5 millimeters out of the one end of tooth 20.
When in use, the wear-resistance of the steel body of the tooth is low compared to that of the tungsten carbide pins. The exposed steel abrades faster than does the exposed carbide 9 resulting in the pins protruding further and further out of the body of the tooth. Some of the pins will break 30 off when the shear force becomes too great. However, as the wear continues, the broken pins begin to again protrude from the body of the tooth. A more wear-resistant alloy for the body of the tooth would not change this self-compensating mode of wear, but only slow down the process. On the other 35 hand, the spacing between pins controls the rate of wear g between them. It is the combination of the material utilized in the body of the tooth, and the size and relative spacing of the carbide pins which determines the tooth wear rate, i.e.
the tooth's ability to penetrate without excessive stressing of protruding carbide pins. The choice of the material for the body of the tooth and the carbide pins determines the strength and overall wear-resistance of the teeth; however, pin spacing governs the ability of the teeth to penetrate the face of the ditch. In effect, a pair of counteracting considerations are present. If the spacing of the pins is too close then penetration of the ditch face will be hampered due to inadequate pin protrusion. Harder soils require greater penetration of the teeth and thus wider spacing between the carbide pins, but such wider spacing generates greater wear on the body of the teeth and thus tends to result in greater breakage of the pins. The foregoing considerations and casting practicalities dictated the final positioning of the four pins in the teeth. As earlier discussed, each pin 30 is approx-irately 75 millimeters long and, of that length, approximately 7 to 8 millimeters protrudes from the body of the tooth. The maximum theoretical wear length is 60 to 65 molters. If the tooth is positioned on the bucket such that the rake angle is 25, as earlier discussed, then the area of the wear surface of the tooth remains almost constant over its entire usable length.
Claims (15)
1. A tooth adapted to be mounted on a bucket of the digging wheel of a wheel-type ditching machine, the tooth having a first end and a second end, the first end being angularly offset from the second end, the first end having means for connecting the tooth to the bucket, the second end having a generally U-shaped cross-section comprising a central section and pair of integral outer flange sections positioned generally perpendicular thereto, the central section extending generally perpendicular to the angle of offset, the flange sections also connecting integrally with the first end to provide structural rigidity to the central section of the second end, a series of elongated members extending longitudinally through the central section of the second end, the elongated members being formed from a material having a greater wear-resistance than the material of the remainder of the tooth.
2. A tooth as in claim 1, wherein the first end is configured as a female coupling adapted for complementary engagement with a male coupling connected to the bucket so as to extend forward thereof.
3. A tooth as in claim 1 or 2, wherein the tooth is adapted to be mounted on the bucket such that, when mounted, each of the series of elongated members on the tooth extends at an angle of approximately twenty-five degrees relative to a line extending between the center of the wheel and the tooth.
4. A tooth as in claim 1, wherein the tooth is one of a series of identical teeth adapted to be mounted on the bucket of the wheel such that in one direction around the wheel every third bucket has the teeth mountable thereon in the same configuration, each of the teeth of each third bucket being laterally offset from each of the teeth on the intervening pair of buckets.
5. A tooth as in claim 1, wherein the series of elongated members comprises four cylindrical pins in planar alignment, the pins extending in parallel spaced relation longitudinally through the central section of the second end.
6. A tooth as in claim 5, wherein each pin is formed from a composition being approximately 84% tungsten carbide and 16%
cobalt.
cobalt.
7. A tooth as in claim 5, wherein each pin is approximately 75 millimetres long and approximately 10 millimetres in diameter.
8. A tooth as in claim 1, wherein the material of the remainder of the tooth is formed from an iron alloy composition having a nickel content by weight approximately between 2.5 per cent and 3.25 per cent.
9. A tooth as in claim 1, wherein the material of the remainder of the tooth is formed from an iron alloy composition having a carbon content by weight approximately between 0.16 per cent and 0.22 per cent.
10. A tooth as in claim 1, wherein the material of the remainder of the tooth is formed from an iron alloy composition having a manganese content by weight approximately between 0.6 per cent and 1.0 per cent.
11. A tooth as in claim 1, wherein the material of the remainder of the tooth is formed from an iron alloy composition containing carbon, manganese, silicon, nickel, chromium and molybdenum.
12. A process for manufacturing a tooth adapted to be mounted on a bucket of the digging wheel of a wheel-type ditching machine, the tooth being of the type having a series of elongated members of high wear-resistance extending in a longitudinal direction therethrough, the process comprising the steps of:
(a) positioning a series of extended elongated members, each approximately twice the length of the elongated members such that they extend into a adjacent pair of cavities for forming two such teeth, one end of each extended elongated member extending into one cavity and the other end of each extended elongated member extending into the other cavity;
(b) casting the teeth with the extended elongated members in that position such that, after casting the teeth are connected only by the extended elongated members extending therebetween; and, (c) dividing each extended elongated member into two parts generally centrally of its length, after the casting, such that one portion of each extended elongated member extends as an elongated member from one tooth and the other portion extends as an elongated member from the other tooth.
(a) positioning a series of extended elongated members, each approximately twice the length of the elongated members such that they extend into a adjacent pair of cavities for forming two such teeth, one end of each extended elongated member extending into one cavity and the other end of each extended elongated member extending into the other cavity;
(b) casting the teeth with the extended elongated members in that position such that, after casting the teeth are connected only by the extended elongated members extending therebetween; and, (c) dividing each extended elongated member into two parts generally centrally of its length, after the casting, such that one portion of each extended elongated member extends as an elongated member from one tooth and the other portion extends as an elongated member from the other tooth.
13. A process as in claim 12, wherein each extended elongated member has a circumferential groove formed at approximately the mid-point of its length, the groove defining a region of weakness and facilitating the dividing of each extended elongated member into two parts.
14. A process as in claim 12, wherein the series of elongated members comprises four cylindrical pins in planar alignment, the pins extending in parallel spaced relation through one end of the tooth.
15. A process as in claim 12, 13 or 14 wherein each outer end of each extended elongated member is generally conical-shaped.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000443237A CA1211136A (en) | 1983-12-14 | 1983-12-14 | Wheel ditcher tooth |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000443237A CA1211136A (en) | 1983-12-14 | 1983-12-14 | Wheel ditcher tooth |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1211136A true CA1211136A (en) | 1986-09-09 |
Family
ID=4126744
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000443237A Expired CA1211136A (en) | 1983-12-14 | 1983-12-14 | Wheel ditcher tooth |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1211136A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2692428A1 (en) * | 1992-06-15 | 1993-12-24 | Kennametal Inc | Basement penetration plates. |
| WO2009061248A1 (en) * | 2007-11-09 | 2009-05-14 | Combi Wear Parts Ab | Self- sharpening, auto- signalling wearing part |
-
1983
- 1983-12-14 CA CA000443237A patent/CA1211136A/en not_active Expired
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2692428A1 (en) * | 1992-06-15 | 1993-12-24 | Kennametal Inc | Basement penetration plates. |
| WO2009061248A1 (en) * | 2007-11-09 | 2009-05-14 | Combi Wear Parts Ab | Self- sharpening, auto- signalling wearing part |
| US7930844B2 (en) | 2007-11-09 | 2011-04-26 | Combi Wear Parts Ab | Self-sharpening, auto-signalling wearing part |
| CN101889118B (en) * | 2007-11-09 | 2012-08-15 | 康比磨损部件股份有限公司 | Self- sharpening, auto- signalling wearing part |
| EA018287B1 (en) * | 2007-11-09 | 2013-06-28 | Комби Веар Партс Аб | Self-sharpening, auto-signalling wearing part |
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| Date | Code | Title | Description |
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| MKEX | Expiry |