Abstract:
Wear resistors adapted for use in wear parts comprising steel castings for replaceable attachment to snow plows, road machinery equipment, agriculture, and construction excavator teeth. The wear castings provide a replaceable member for wear affected parts of equipment used for cutting, scraping, digging, plowing, etc. Each replaceable wear part can comprise a hard, impact resistant metal of high shear strength having at least one cavity filled with an abrasion resistant weldment or resistor. The abrasion resistant weldment can be placed proximal to the wear edges or wear surfaces of the expendable and replaceable wear parts.

Description:
BACKGROUND 
       [0001]    This application relates to snow plows, agriculture equipment, construction excavator teeth, and other road machinery, and more specifically to guards, and wear resistors for the wear surfaces, i.e. blades and teeth, thereof. 
         [0002]    Usually the heavy steel cutting or wear edges of blades, teeth, and skid shoes are expendable and can be removable, e.g., with bolts, to the bottom of, for example, a plow moldboard, backhoe bucket, grinder wheel, etc. As a blade scrapes along the pavement or ground it wears. The wear often is uneven, and the blades and teeth (cutting edges) sometimes break during plowing, digging, scraping, etc. All this maintenance and the associated downtime are costly. 
         [0003]    The blade on typical snow plowing machines is subjected to extensive vibration, impact, and abrasive action, resulting from the scraping action between the cutting edge of the blade and the roadbed over which the machine travels. As a result, the blade edge wears and chips due to the road abrasion and impact and must be replaced every few hours. This is a costly proposition because of the down time of the machine and cost expended in manpower and materials to make a blade changeover. 
         [0004]    It is conventional to provide to the plow or plow attachment frame caster-like wheels, mushroom shoes, or wear skid shoes which are attached to, but spaced from, the plow moldboard for the purpose of supporting part of the load on the blade. These known prior art devices are relatively bulky, expensive to manufacture, and difficult to install on the snow plow. The cast iron material typically used on the wear shoes does not provide protection against fracturing or breakage, due to the relative brittleness of cast iron, when the shoes are subjected to impacts. The shoes are expensive to maintain and replace. 
         [0005]    Thus, there has been a need for an improved means which supports the cutting edge of, for example, a snow plow blade from the roadbed for reducing or dampening the undesirable vibrating, impact and abrasive action on the blade. The disadvantages of present wear shoe constructions have resulted in the improved skid shoe-wear surface of the present disclosure which effectively reduces blade wear and shoe replacement resulting from road abrasion. Furthermore, the present disclosure can increase blade (cutting edge) life, skid shoe life, reduce blade breakage and maintenance, and protect the moldboard, bucket or similar mounted thereto. 
         [0006]    In one embodiment, the present disclosure relates to a skid shoe for a snow plow blade, and more particularly, to a shoe which is bolted to the plow moldboard at the pre-existing bolt holes used to fasten the blade to the moldboard. Alternatively, the skid shoe can be mounted to the plow attachment frame. The skid shoe can include a wear surface including an abrasion resistant welding deposit filling one or more cavities along, and integrated with, the wear surface. In other embodiments, the present disclosure provides wear resistors embedded within blades and teeth for improved wear resistance along the associated cutting edges. 
       SUMMARY 
       [0007]    One aspect of this disclosure provides an expendable wear part adapted for replaceable attachment to, for example, a snow plow blade or other mounting attachment of an associated component of road machinery. The wear part comprises a steel casting having a mounting surface and a wear surface. The wear surface has at least a first cavity extending along and below the wear surface. The at least first cavity includes an abrasion-resistant welding deposit therein for extending the service life of the wear surface of the wear part. The deposit comprises a weldment material selected from the group consisting of chrome carbide, vanadium carbide, and tungsten carbide. The weldment material can have a higher hardness than the steel casting. 
         [0008]    Another aspect of the disclosure provides for an expendable wear part adapted for replaceable attachment. The wear part comprises a steel casting. The wear part includes a direction of travel when in an engaged position. The steel casting includes a wear surface having a plurality of cavities extending along the wear surface. The plurality of cavities each have an abrasion-resistant welding deposit therein. The welding deposit has a higher hardness than the steel casting. The welding deposits in the plurality of cavities overfills the cavities and forms substantially parallel bulbous deposits adjacent to and extending outwardly from the wear surface of the casting. The deposits can be longitudinally aligned with, or transverse to, the direction of travel. 
         [0009]    Yet another aspect provides a method for extending the life of an expendable wear part adapted for replaceable attachment. The method comprises casting a steel wear part having a plurality of cavities extending longitudinally along a wear surface of the wear part. The method further comprises welding a series of abrasion resistant deposit layers in the cavities wherein the layers are spaced from one another and run along the majority of the length of the wear surface of the casting and wherein the deposit layers have a higher hardness than the steel casting wear part. The cavities can be aligned with, or transverse to, a direction of travel of the wear part when the wear part is in an engaged and use position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a perspective view of a snow plow blade equipped with a pair of skid shoe-wear resistor combinations of the present disclosure according to a first embodiment; 
           [0011]      FIG. 2  is a cross sectional view of the skid shoe taken along line  2 - 2  of  FIG. 1 ; 
           [0012]      FIG. 3  is a top plan view of the skid shoe according to the first embodiment; 
           [0013]      FIG. 4  is a front elevational view of the skid shoe  FIG. 3 ; 
           [0014]      FIG. 5  is a bottom plan view of the skid shoe illustrating the spatial relationship between the wear surface and the wear resistors; 
           [0015]      FIG. 6  is a cross sectional view of the skid shoe taken along line  6 - 6  of  FIG. 4 ; 
           [0016]      FIG. 7  is a side plan view of a snow plow blade and frame attachment equipped with a skid shoe wear resistor of the present disclosure according to a second embodiment; 
           [0017]      FIG. 8  is a top plan view of the skid shoe according to the second embodiment; 
           [0018]      FIG. 9  is a partial cross sectional side view of the skid shoe according to the second embodiment; 
           [0019]      FIG. 10  is a bottom plan view of the skid shoe wear resistor illustrating the spatial relationship between the wear surface and the wear resistors; 
           [0020]      FIG. 11  is a cross sectional view of the skid shoe taken along line  11 - 11  of  FIG. 9 ; 
           [0021]      FIG. 12  is a side plan view of a snow plow blade and frame attachment equipped with a skid shoe wear resistor of the present disclosure according to a third embodiment; 
           [0022]      FIG. 13  is a top plan view of the skid shoe according to the third embodiment; 
           [0023]      FIG. 14  is a partial cross sectional side view of the skid shoe taken along line  14 - 14  of  FIG. 13 ; 
           [0024]      FIG. 15  is a bottom plan view of the skid shoe wear resistor illustrating the spatial relationship between the wear surface and the wear resistors; and, 
           [0025]      FIG. 16  is a cross sectional view of the skid shoe taken along line  16 - 16  of  FIG. 13 . 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    In a first embodiment, the wear resistant surface made in accordance with the teachings of the present disclosure is illustrated in  FIGS. 1-6 . A skid or moldboard shoe  10  can be used to reduce the extensive vibration, impact, and abrasive action between the cutting edge of a snow plow blade and the associated skid shoes along the roadbed  3  over which the snow plow travels. In one mounting arrangement, a pair of skid shoes or moldboard shoes  10  can be mounted on opposite ends of the blade, as illustrated in  FIG. 1 . 
         [0027]    The skid shoe  10 , according to a first embodiment, includes a mounting plate  12  which is secured to the backside of a conventional snow plow blade  18  at the pre-existing bolt holes  16  used to fasten a cutting edge  20  and a moldboard  15  such that shoe  10  can be mounted close to the cutting edge  20  of snow plow blade  18 . One of the advantages of the moldboard shoe  10  is that it can be mounted to mounting structure  14  using longer bolts  22  and the same bolt openings  16  which are used in securing cutting edge  20  to moldboard  15 . Thus, the present construction eliminates complicated and bulky supporting structure for the skid shoe  10 , thereby reducing the time and cost of fitting the skid shoe  10  onto the snow plow blade  18 . Further, the bolts  22  for mounting moldboard  15 , moldboard shoe  10  and structure  14  become shock and impact absorbers for the cutting edge  20  of snow plow blade  18 . 
         [0028]    It is to be appreciated that the bolt mounting openings  16  for snow plow blade  18  are located along moldboard  14  at standard spacings of 8-inch or 12-inch centers. As shown, the mounting plate  12  includes a set of spaced apart mounting openings  24  and  26 , respectively, such that moldboard shoe  10  may be mounted to the snow plow blade  18  having a 12-inch bolt hole center. Other standard mounting hole spacings are also within the scope of the present disclosure. 
         [0029]    The moldboard shoe  10  further includes a generally horizontal skid or wear surface  30 . One or more cavities  40 ,  42  are cast into the moldboard shoe  10  at the time of casting. The moldboard shoe  10  can be cast from steel for greater strength and resiliency. 
         [0030]    In one mounting arrangement, the skid shoe  10  resides close to the blade cutting edge  20  and thus is a more integral part of the blade  18  and, therefore, capable of absorbing more of the undesirable abrasive wear. 
         [0031]    The steel casting can take on the following analysis (balance iron). 
         [0000]    
       
         
               
               
               
               
               
               
               
               
             
           
               
                   
               
             
             
               
                 C 
                 Mn 
                 P 
                 S 
                 Si 
                 Cr 
                 B 
                 Hardness Bhn 
               
               
                 ×100 
                 ×100 
                 ×1000 
                 ×1000 
                 ×100 
                 ×100 
                 ×100 
                 363/401 
               
               
                 16 
                 140 
                 16 
                 16 
                 525 
                 26 
                 0.4 
               
               
                   
               
             
          
         
       
     
         [0032]    The greater the impact resistance, shear strength, and hardness of the panel sections, generally the better. Accordingly, armor steel castings can be used, typically ones with high chromium, carbon and silicon contents. Other armor steels, quenched and tempered ultraservice steels, and maraging steels also are useful here. The casting process can include the provision of one or more cavities  40 ,  42  in association with the wear surface  30 . 
         [0033]    Subsequent to casting, the cavities  40 ,  42  can be filled and/or overfilled by welding therein a layered carbide matrix. The layered carbide matrix can be composed of a series of layered deposits  50 ,  52 , one on top of another until the cavity is filled or overfilled. Overfilling the cavity can result in a convex or bulbous layer  60 ,  62  of carbide matrix terminating beyond, i.e. extending below, the wear surface  30  of the shoe  10 . The matrix provides a reconstitutable embedded weldment or resistor  50 ,  52  for increased wear resistance of the wear surface  30 . In one exemplary embodiment, the two longitudinal cavities  40 ,  42  extend along substantially the length of the wear surface  30 . The cavities  40 ,  42  can be spaced from one another and proximal to opposing edges  44 ,  46 , respectively, of the shoe  10 . Referring now to  FIG. 6 , there is shown a wear termination or replacement line  56 . The wear replacement line  56  indicates when the shoe  10  should be replaced. The wear line  56  can be reached, for example, when all, or substantially all, of the carbide matrix has worn off which can correspond to approximately 25% of wear of the steel casting skid shoe  10 . 
         [0034]    The weldments  50 ,  52  can comprise a weight of between 1 and 4 pounds. The weldments  50 ,  52  can increase the weight of each shoe from about 5% to about 20%. The plurality of weldments  50 ,  52  can be aligned with the wear surface  30  such that when the plow is in use and traveling along the road surface, the weldments  50 ,  52  are transverse to the direction of travel. Alternatively, the weldments can be aligned such that they are aligned with the direction of travel. 
         [0035]    The weld deposits  50 ,  52  can have the following analysis (balance iron): 
         [0000]    
       
         
               
               
               
               
               
               
             
           
               
                   
               
             
             
               
                 C 
                 Cr 
                 Mo 
                 Si 
                 Mn 
                 Hardness/Rc 55-60 
               
               
                 ×100 
                 ×100 
                 ×100 
                 ×100 
                 ×100 
               
               
                 2.60 
                 12.00 
                 0.62 
                 1.37 
                 0.77 
               
               
                   
               
             
          
         
       
     
         [0036]    Conventional hard-facing or wear-facing weldments can be used for the deposits. So-called chrome carbide steels are the most common, e.g., Stoody Company No. 121, although vanadium carbide (Stoody No. 134) and tungsten carbide ones also can be used very effectively. It is to be appreciated that the weldment material deposited in the cavity has a higher hardness than the steel casting. 
         [0037]    The weldment metal must be abrasion-resistant. Generally, it is a high chrome ferrous metal weld. It is reconstitutable in the sense that it can be repaired or replaced by redeposition of carbide matrix by welding. 
         [0038]    The wear surface  30  and the embedded or integrated weldments  50 ,  52  help to support the cutting edge  20  of the blade such that the abrasive action and impact from the roadbed  3  works on the wear surface  30  and weldments  50 ,  52  of the skid or moldboard shoes  10  instead of the blade cutting edge  20 , thereby substantially prolonging the life of the cutting edge  20 . In addition, the weldments  50 ,  52  substantially prolong the life of the associated shoe  10  due to the wear surface  30  being a combination of carbide matrix and steel casting. The present wear resistors are intended to perform better than mechanically fastened solid carbide bars would under the extreme conditions of vibration, impact and thermal shock experienced by snow plow blades. 
         [0039]      FIGS. 7-11  show another embodiment of the skid shoe  110 . This shoe  110  is a rectilinear shoe with angled fore and aft surfaces  114 ,  116  and a planar bottom wear surface  130 . A pair of cavities  140 ,  142  are shown with weldments  150 ,  152  deposited therein. Referring now to  FIG. 9 , there is shown a wear termination or replacement line  156 . The wear replacement line  156  indicates when the shoe  110  should be replaced. The wear line  156  can be reached, for example, when all, or substantially all, of the carbide matrix has worn off which can correspond to approximately 25% of wear of the steel casting skid shoe  110 . 
         [0040]    The surface area of the weldments  150 ,  152  can comprise from about 20% to about 30% of the total surface area of the bottom wear surface  130 . 
         [0041]    The expendable wear parts or shoes I  10  are adapted for replaceable attachment to, for example, a snow plow mold board or snow plow mounting arrangement  170  ( FIG. 7 ). The at least first cavity  140  can include an abrasion-resistant welding deposit  150  therein for extending the service life of the wear surface  130  of the wear part. The wear part can include the second cavity  142  substantially aligned with the first cavity  140 . The second cavity  142  can include the abrasion-resistant welding deposit  152  therein for further extending the service life of the wear surface  130 . The welding deposits can comprise the matrix structure as described above. The cavities  140 ,  142  can be refilled in order to extend the life of the wear part. In this manner, the weldments  150 ,  152  can be reconstituted before the wear surface  130  reaches the wear line  156 . The first and second cavities can be substantially parallel to one another. 
         [0042]    It is to be appreciated that skid shoe  110  includes a set of spaced apart mounting openings  124  and  126  such that shoe  110  may be mounted to the snow plow mounting frame  170 . Other standard mounting hole spacings and arrangements are also within the scope of the present disclosure. 
         [0043]    The welding deposits  150 ,  152  in the first and second cavities  140 ,  142  can overfill the cavities forming substantially parallel bulbous deposits  160 ,  162  extending outwardly from the wear surface  130  of the casting (see  FIG. 11 ). The first and second cavities  140 ,  142  can be spaced from one another and run along the majority of the length of the wear surface  130  of the casting (refer to  FIG. 10 ). The cavities  140 ,  142  can be proximal to opposing edges  144 ,  146 , respectively, of the shoe  110 . 
         [0044]    The wear part  110  can include a thickness  134  between the wear surface  130  and an upper surface  132  of the shoe  110 . The first and second cavities  140 ,  142  can include a depth  143 ,  145  wherein the depth is at least one half of the thickness  134  of the wear part  110 . 
         [0045]    In one exemplary shape, the essentially flat or panel portion of each shoe  110 , as shown in  FIGS. 7-11 , can be about 12 inches long, 7 inches wide, and 1¼ inch thick armor steel It is to be appreciated that other embodiments can take the form of other shapes and other dimensions. 
         [0046]    In another exemplary embodiment ( FIGS. 12-16 ), a so-called mushroom skid shoe  210  is shown. This shoe  210  comprises a circular shape with a circumferential bottom wear surface  230 . A pair of cavities  240 ,  242  are shown with weldments  250 ,  252  deposited therein. Referring now to  FIG. 14 , there is shown a wear termination or replacement line  256 . The wear replacement line  256  indicates when the shoe  210  should be replaced. The wear line  256  can be reached, for example, when all, or substantially all, of the carbide matrix is worn off which can correspond to approximately 25% of wear of the steel casting skid shoe  230 . 
         [0047]    The surface area of the weldments  250 ,  252  can comprise from about 20% to about 30% of the total surface area of the bottom wear surface  230 . 
         [0048]    The expendable wear parts or shoes  210  are adapted for replaceable attachment to, for example, a snow plow mold board or snow plow mounting arrangement  270  ( FIG. 12 ). The at least first cavity  240  can include an abrasion-resistant welding deposit  250  therein for extending the service life of the wear surface  230  of the wear part. The wear part can include the second cavity  242  substantially aligned with the first cavity  240 . The second cavity  242  can include the abrasion-resistant welding deposit  252  therein for further extending the service life of the wear surface  230 . The welding deposits can comprise the matrix structure as described above. The cavities  240 ,  242  can be refilled in order to extend the life of the wear part  210 . In this manner, the weldments  250 ,  252  can be reconstituted before the wear surface  230  reaches the wear line  256 . The first and second cavities  240 ,  242  can be substantially parallel to one another. 
         [0049]    It is to be appreciated that skid shoe  210  includes a set of spaced apart mounting openings  224  and  226  such that shoe  210  may be mounted to the snow plow mounting frame  270 . Other standard mounting hole spacings and arrangements are also within the scope of the present disclosure. 
         [0050]    The welding deposits  250 ,  252  in the first and second cavities  240 ,  242  can overfill the cavities forming substantially parallel bulbous deposits  260 ,  262  extending outwardly from the wear surface  230  of the casting. The first and second cavities  240 ,  242  can be spaced from one another and run along the majority of the length of the wear surface  230  of the casting (refer to  FIG. 15 ). 
         [0051]    The wear part  210  can include a thickness  234  between the wear surface  230  and an upper surface  232  of the shoe  210 . The first and second cavities  240 ,  242  can include a depth  243  wherein the depth is at least one half of the thickness  234  of the wear part  210 . 
         [0052]    In one exemplary shape, the essentially circular skid shoe  210 , as shown in  FIGS. 12-16 , can be about 12 inches in circumference overall including a wear surface  230  having a circumference of about 8 inches. It is to be appreciated that other embodiments can take the form of other shapes and other dimensions. 
         [0053]    When the wear parts comprise a plow skid shoe, a pair of skid shoes  10 ,  110 ,  210  are typically provided for attachment to opposite ends of a blade or opposing sides of a snow plow attachment frame  14 ,  170 ,  270  whereby the wear surface  30 ,  130 ,  230  of each plow skid shoe  10 ,  110 ,  210  is simultaneously in sliding engagement with a road surface  3  during use thereof. Thus, the pair of shoes  10 ,  110 ,  210  provide the majority of total wear surface when the plow vehicle is in use. 
         [0054]    The wear part includes a direction of travel when an associated plow is in an engaged and use position. The deposits  50 ,  52 ,  150 ,  152 ,  250 ,  252  can be longitudinally aligned with, or transverse to, the direction of travel. The plurality of cavities  40 ,  42 ,  140 ,  142 ,  240 ,  242  can be spaced from one another and run along the majority of the length of the wear surface  30 ,  130 ,  230  of the castings ( FIGS. 5 ,  10 ,  15 ). 
         [0055]    The method of welding the deposits can include depositing the matrix layers one on top of another wherein each individual layer running along substantially the length of the cavity. It is to be appreciated that the weldments  50 ,  52 ,  150 ,  152 ,  250 ,  252  can be reconstituted prior to the wear surface reaching the wear line. 
         [0056]    Although not illustrated, the present disclosure also relates to excavating and other agriculture tools such as revolving cutter head excavators for use in mines or dredgers. The wear surfaces can be, for example, on the cutting teeth or scrapers therefore. 
         [0057]    Revolving cutter head excavators consist of a drive wheel that rotates around a shaft and is driven by a means of rotation. The periphery of the revolving cutter head excavator has a series of buckets equipped with teeth arranged in directions that are essentially radial. Dredgers do not have buckets and their teeth are distributed around the periphery in a rotary ogival structure. Each tooth consists of a single-unit tooth body structure made of a mechanically resistant metal or alloy such as steel, having a fixing area to connect it to the bucket or the ogival structure and a working area to dig the soil. The working area is generally flat and shaped like a shovel and is bounded by a leading face that points in the direction of movement of the periphery of the wheel or ogival structure in the preferred direction of rotation and a trailing face or face opposite the leading face. The leading face and the trailing face are generally flat or slightly curved and are connected by a front tapered facet that defines a transverse cutting edge. If the tooth is mounted on the bucket or the ogival structure, the transverse cutting edge is essentially parallel to the axis of rotation of the assembly and the general plane formed by the tooth shovel or working area generally slants in the direction of the direction of movement of the tooth in the preferred direction of rotation. 
         [0058]    During operation, part of the peripheral zone of the bucket or cutter cuts into the ground, the transverse cutting edge of the teeth bites into the ground and the leading face pushes up the material. This results in considerable wear of the transverse cutting edge and the leading face. 
         [0059]    One common solution to increase the service life and the efficiency of the teeth is to hardface the external surface of the leading face and the tapered front facet in order to cover them with a coat of molten carbide by fusing a welding bead. 
         [0060]    Although this process significantly increases the service life of the tooth, wear still occurs, relatively slowly at the start of use when the hard material still covers the front facet; wear then becomes much faster when the hard material that covers the front facet is itself damaged by wear. The tooth can only be used as long as the length of its working area has not reduced too extensively and this defines the maximum permissible area of wear of the tooth. 
         [0061]    In particular, as soon as the front facet has lost its protective coating of hard material, wear becomes much faster despite the existence of a layer of hard material on the leading face of the tooth. 
         [0062]    Dredger teeth with a composite structure are known consisting of a metal tooth body containing inserts of a hard anti-abrasion material. In document U.S. Pat. No. 3,805,423, a prefabricated insert is fitted in appropriate recesses in the metal tooth body where it is fixed by welding or brazing. The insert, in the embodiment shown in  FIGS. 3 and 4 , consists of two intermediate bars which each take up half the height of the tooth. Document U.S. Pat. No. 4,052,802 also describes providing a prefabricated insert and fitting it in the tooth body. The insert is sandwiched between the metal surface plates, between which it is assembled by brazing. Therefore the insert does not take up the entire height of the tooth. There is no suggestion in this document of replacing the metal plates by a material containing particles of a hard material. 
         [0063]    In contrast to providing prefabricated inserts, the present disclosure, similar to the above description for skid shoes, provides for a steel casting with one or more cavities. The cavities can be transverse to the cutting edge of the teeth and extend along a majority of the length of the teeth. Each of the cavities can subsequently be filled with a carbide matrix by way of welding layers of deposits according to the detailed description provided above. 
         [0064]    While particular embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or may be presently unforeseen may arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they may be amended are intended to embrace all such alternatives, modifications variations, improvements, and substantial equivalents.