Patent Publication Number: US-7707753-B2

Title: Multifunctional plow blade positioning apparatus and method

Description:
RELATED APPLICATIONS 
   The present application is (1) a continuation-in-part of U.S. patent application Ser. No. 10/841,740, filed on May 7, 2004, which is a continuation of U.S. patent application Ser. No. 10/404,164, filed Mar. 31, 2003, now U.S. Pat. No. 6,817,118, which claims benefit of PCT/US01/47125, filed Nov. 12, 2001; (2) a continuation-in-part of U.S. patent application Ser. No. 10/850,151, filed on May 19, 2004, now U.S. Pat. No. 7,131,221, which is a continuation-in-part of U.S. patent application Ser. No. 10/404,164, filed Mar. 31, 2003, now U.S. Pat. No. 6,817,118, which claims benefit of PCT/US01/47125, filed Nov. 12, 2001; and (3) a continuation-in-part of U.S. patent application Ser. No. 10/990,148, filed on Nov. 15, 2004, which is a continuation of U.S. patent application Ser. No. 10/404,164, filed Mar. 31, 2003, now U.S. Pat. No. 6,817,118, which claims benefit of PCT/US01/47125, filed Nov. 12, 2001, all of which are herein incorporated by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to adjustable snow plows for attachment to land vehicles, primarily personal utility vehicles such as pickup trucks and sport utility vehicles. 
   BACKGROUND OF THE INVENTION 
   Moving snow off of open ground, streets, sidewalks and parking lots is an age-old problem in less temperate climates where significant snowfall is anticipated during colder periods of the year. For instance, in many parts of Canada and in many northern states in the United States, significant snowfall can be expected during the late fall and early-to-mid winter months, and again in the late winter and even, at times, early spring. 
   Clearing freshly fallen snow from open ground, parking lots, driveways, sidewalks and roadways, whether these surfaces are paved or not, is a task common to all of these areas that is generally required to make these surfaces safe and passable, both initially and over time if the snow begins to build up after multiple snowfalls. If the snow is allowed to accumulate over a period of weeks, the snow eventually makes the use of these surfaces for both pedestrian and vehicular travel difficult, if not treacherous. Therefore, many devices have been designed and manufactured to remove freshly fallen and accumulated snow from such surfaces. 
   Municipalities generally use large vehicles with enormous snow plows to clear paved roadways used by the public, and county and state government public works and transportation departments in these areas also generally have a fleet of these kinds of vehicles to clear snow from roadways and from large parking lots on county-owned or state-owned properties. 
   The purchase and use of such a vehicle by individuals, however, who have a need to move or remove accumulated snow in smaller areas, such as driveways and privately owned parking areas, is less feasible. First of all, the larger vehicles are expensive to purchase and maintain and are, in some cases, dedicated solely to the removal of accumulated snow. It will be appreciated that it would not be cost effective for an individual to purchase, house and maintain such a vehicle for just removing snow from driveways and smaller parking lots during a limited period of the year. Furthermore, these vehicles are difficult to operate and often require significant training or experience operating such vehicles. 
   For this reason, many inventors have designed and manufactured adjustable snow plows that can be attached to pickup trucks and other vehicles for a period of time during the year when snow removal is required. In this way, the vehicles can be used for other purposes during periods when snow removal is not required. 
   Many of the snow plows attached to these vehicles, however, are large and heavy and are not easily attached and removed from the vehicles. A number of snow plows have been invented that attempt to address these problems. For instance, Kowalczyk (U.S. Pat. No. 4,944,104) discloses a detachable snow plow assembly that is pivotally attached to a common passenger vehicle. In one embodiment of the invention, the snow plow includes rollers secured within attachment channels attached to mounting uprights to allow the plow blade to ride up and down when the blade comes into contact with irregularities in the surface. The plow blade can also pivot forward along with the mounting uprights in certain embodiments when the vehicle is moving backward allowing the plow blade to pivot forward over the ground. In other disclosures, such as the snow plow assembly disclosed by Rosenberg (U.S. Pat. No. 5,136,795), a trip mechanism is disclosed which allows the lower part of the plow blade to pivot backward when the plow blade comes into contact with relatively immovable objects and the trip mechanism is actuated. Rosenberg also discloses a rubber scraper at the bottom of the plow blade which is secured between two metal plates and oriented at an angle rearward of a vertical orientation. Rubber scrapers are also disclosed on older snow plows, such as the snow plow mold board disclosed by C. H. Wagner (U.S. Pat. No. 3,477,149), which discloses a resilient scraping blade made of rubber. This is a common feature in many snow plows, allowing the rubber scraper to contact the ground and provide a somewhat more forgiving surface with which to contact the ground when the plow is used to remove accumulated snow, but the rubber scraper is generally accompanied by a metal backing. 
   Although each of these inventions has its own advantages, none of them are easy to attach to or remove from the vehicle. These snow plows also tend to be heavy and cumbersome, and at least somewhat unsightly if one is required, for practical reasons, to keep it attached to the vehicle 24/7 for a period of several months during the snow season. 
   The present invention provides a more cost effective and attractive snow plow for removing smaller amounts of accumulated snow from driveways and small-to-medium sized parking lots where one individual may wish to use his or her vehicle to remove snow during a relatively limited period of time, while still having use of the vehicle available for other purposes, not involving snow removal, when the snow plow must either be removed from the vehicle and/or placed in a suitable position for non-snow removing transit. 
   In addition, the prior art snow plows are generally so heavy that they will not ride up when they are on open ground, for instance, but will tear up the ground and remove grass and other plant things often just because of the sheer weight of the plow as it passes along the ground surface. Also, the prior art snow plows are often virtually impossible for a single person to handle, because of the weight associated with these plows; and plows that appear to be relatively light weight, such as the snow plow described by Knutson et al. (U.S. Pat. No. 6,240,658), generally have multiple attachment points and do not appear to be highly effective, durable or marketable. 
   The present invention provides solutions for these and other problems associated with the prior art devices for removing accumulated snow and methods used to accomplish the same. 
   SUMMARY OF THE INVENTION 
   The present invention provides a snow plow for attachment to a vehicle, the snow plow including a mounting apparatus having a mounting frame, the mounting frame including a mounting upright. The snow plow further including a plow blade, the plow blade including retention apparatus constructed and arranged to disengageably secure the plow blade to the mounting upright(s) when the plow blade is in a working orientation for use to plow snow. The plow blade preferably includes a mold board, the mold board preferably being an aluminum extrusion having a hollow core that may be subdivided into cells or compartments. In preferred embodiments, the aluminum extrusion will preferably include at least one attachment channel, preferably a plurality of attachment channels, in which parts of the snow blade can be secured or anchored. Preferably, the snow plow is constructed and arranged to slidably secure the plow blade to the mounting uprights when the plow blade is in use. The plow blade preferably includes first and second attachment channels and the retention apparatus preferably includes at least one retention member anchored in at least one of the attachment channels, preferably in both of the first and second attachment channels. 
   In preferred embodiments, the snow plow further includes an elongated strap selectively connectable between the plow blade and the mounting apparatus in at least one position, such as a constrained orientation, wherein the elongated strap resists upward movement of the plow blade when the plow blade is disengageably secured to the mounting apparatus or an elevated orientation, wherein the elongated strap suspends the plow blade a desired distance from the ground to prevent the plow blade from contacting the ground and/or snow on the ground. 
   In certain preferred embodiments, the mounting apparatus further includes an elongated member constructed and arranged to place downward force upon the plow blade when the plow blade is disengageably secured to the mounting uprights during use and the elongated member is a resilient elongated member, preferably a shock cord. In certain embodiments, the self-adjusting snow plow is attached to a vehicle in such a manner to permit the snow plow to make position adjustments when, during use then the vehicle is in motion, a portion of the snow plow comes into contact with a mass of snow or other relatively immovable objects on the ground, upon which the vehicle travels when in motion. The self-adjusting snow plow preferably includes a mounting apparatus for attachment to the vehicle, and a plow blade. The mounting apparatus preferably includes first and second mounting uprights and the plow blade has first and second ends, a top, a bottom, retention apparatus, perhaps a retention member and a rubber scraper, preferably secured to the bottom of the plow blade. In certain embodiments, the retention apparatus will include first and second retention members. In these embodiments, the retention apparatus is generally constructed and arranged to at least partially encircle at least one of the respective mounting uprights when the plow blade is engaged with the mounting apparatus in a working orientation, such that the plow blade is in contact with the ground or objects on the ground. The retention apparatus will preferably include at least one retention member for each mounting upright. The retention members preferably slidably engage the respective mounting uprights when the plow blade is engaged with the mounting apparatus in a working orientation. 
   When the plow blade alternate and preferred embodiments of the present invention come into contact with a mass of snow or other objects on the ground that are relatively immovable, the retention apparatus, preferably the respective retention members, can slide upward along the respective mounting uprights to enable the respective ends of the plow blade to slide upwardly relative to the mounting upright most proximate to that end of the plow blade. The retention apparatus or retention members, in preferred embodiments, permit the bottom of the plow blade to pivot away from the respective mounting uprights when the plow blade is engaged with the mounting apparatus in a working orientation and the vehicle is in motion in a direction rearward of the plow blade. In certain embodiments, the rubber scraper secured to the bottom of the plow blade is a resilient elastomeric member having a resting orientation in which the rubber scraper extends downwardly and away from the bottom of the plow blade at an angle which extends forward from a plane which extends along a main surface of the plow blade. In certain of these embodiments, the rubber scraper is preferably about an inch thick and extends away from the plow blade at least about three and one-half inches. 
   It is a primary objective of the present invention to provide a method of clearing accumulated snow from the surface of driveways, parking lots and other similar areas where snow removal is essential during the winter months. 
   It is an additional objective of the present invention to provide such an apparatus that can be easily mounted and removed from the front end of pickup trucks, sport utility vehicles, all-terrain vehicles and other commonly used personal transit type vehicles, and that the apparatus for mounting the plow blade provides flexibility for mounting the plow blade at different relative heights with respect to vehicles that may stand at different relative heights off of the ground. 
   It is a further objective of the present invention to provide such an apparatus for snow removal that is much simpler to install and use then other similar devices commonly found in the market today. 
   It is a further objective of the present invention to provide such an apparatus for snow removal which includes a plow blade which is relatively light and allows an individual person to lift respective ends of the plow blade in order to lower them into position for clearing snow or to lift the respective ends of the plow blade to secure the blade in position for transit, while still providing a durable plow made of materials strong enough to stand up to heavy use during the months in which snow plowing is required. 
   It is a further objective of the present invention to provide such an apparatus for snow removal that does not require the owner of the vehicle to purchase separate running lights for the vehicle in order to use the self-adjusting snow plow. 
   It is yet another objective of the present invention to provide such an apparatus for snow removal that easily slides upward on a mounting apparatus to allow the plow blade to go up and over immovable objects encountered during use. 
   It is a further objective to provide a plow blade that is essentially hinged to the mounting apparatus to permit rapid retreat for the convenience of the user. 
   It is yet another objective of the present invention to provide such an apparatus for snow removal that allows the operator to drive in reverse after moving snow off of a flat surface, wherein the plow blade is able to “float” freely on a pair of mounting uprights and can slide up and down independently on the mounting upright(s), and wherein the lower portion of the plow blade can pivot forward with respect to the mounting uprights allowing the vehicle to easily draw the plow blade in reverse. 
   It is yet another objective of the present invention to provide such an apparatus for snow removal that lifts the rubber scraper at the bottom of the plow blade off the ground when the vehicle draws the plow blade in reverse and the lower portion of the plow blade pivots forward with respect to the mounting apparatus. 
   It is still a further objective of the present invention to provide such a method that does not employ the use of expensive and heavy hydraulic systems that are commonly used in such devices today. 
   Although other vehicle accessory connection devices can be used, these objectives are preferably accomplished by the use of a common hitch receiver that is attached to (and extends forward from) the front end of the vehicle that is to be used in the plowing operation. This receiver hitch preferably provides a mounting point for the mounting apparatus, which is preferably accomplished by inserting a tongue of the plow hitch into the hitch receiver and then locking it into place with a pin. This forms a solid mounting for the present invention that allows it to be quickly and easily attached to the front end of any vehicle. A primary advantage of this invention is that it does not require that a user keep the plow assembly on the plow vehicle for the entire season. Its ease of use is also a primary advantage as is its moderate cost. 
   It is a further objective of the present invention to provide a system for placing downward force on the plow blade when the plow blade is in use, preferably a resilient elongated apparatus for placing downward force on the plow blade as a substitute for constructing the plow blade out of heavy materials which would be difficult for an individual to lift. 
   It is yet another objective of the present invention to provide a method of placing downward force upon the plow blade during snow plowing operations, preferably a method of providing an elongated member, preferably a resilient elongated member, interconnected between the mounting apparatus and the plow blade such that the elongated member places a sufficient amount of downward force on the plow blade during snow plow operations to improve the usefulness of the plow blade in removing snow during such operations, particularly when the plow blade comes into contact with heavy snows that might otherwise begin to cause the plow blade to ride up on the respective mounting uprights. 
   It is yet another objective of the present invention to provide an interconnection system for interconnecting the mounting apparatus of the present snow plow to a vehicle that includes a simple swivel apparatus that can pivot horizontally to permit the plow blade to be turned either to the left or to the right of an angle generally perpendicular to the direction of travel of that of the vehicle pushing the plow blade. 
   It is still another objective of the present invention to provide a mounting apparatus including at least one mounting upright, the mounting uprights preferably including attachment members for securing the plow blade when the plow blade is not in use for snow plowing operations and the vehicle is used for transit purposes. It is a further object to provide attachment members that allow the plow blade to be easily lifted, one end at a time, and secured in the respective attachments members one end at a time, so that a single individual can easily lift the plow blade up into the non-operational use position without assistance. 
   It is yet another objective of the present invention to provide a plow blade including a mold board having attachment channels in which functional parts of the plow blade may be anchored or secured, preferably by securing anchoring nuts within the attachment channel, or attachment channels, in which to secure reciprocally threaded bolts that anchor or secure the functional parts of the plow blade within the attachment channel or channel, such as retention apparatus, preferably a retention member or retention members, a handle or handles for lifting the plow blade and/or hook apparatus, such as a hook or hooks for interconnecting the plow blade to an elongated member attached to the mounting apparatus to provide a downward force on the plow blade during use for snow plowing operations. 
   It is yet a further objective of the present invention to provide a plow blade utilizing a mold board including a first and second piece. Preferably, the first and second pieces are interconnected. A two piece construction is more efficient to produce since it requires a smaller die that is available at a greater number of manufacturing facilities. 
   These and other objectives and advantages of the invention will appear more fully from the following description, made in conjunction with the accompanying drawings wherein like reference characters refer to the same or similar parts throughout the several views. And, although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, in which corresponding reference numerals and letters indicate corresponding parts of the various embodiments throughout the several views, and in which the various embodiments generally differ only in the manner described and/or shown, but otherwise include corresponding parts; 
       FIG. 1  is a side elevation of an embodiment of the present invention showing a self-adjusting snow plow  10 , with the plow blade  30  in a working or operational orientation, attached to a vehicle  18  (shown in phantom); the plow blade  30  is also shown in phantom in an elevated position; 
       FIG. 2  is a partial side elevation of the self-adjusting snow plow  10  shown in  FIG. 1  showing the plow blade  30  in a position in which the bottom (not shown) of the plow blade  30  is pivoted forward so that a retention member  38 , secured to the mold board  32  of the plow blade  30 , can be disengaged from the mounting upright  20  and placed in the attachment member  51  so that the plow blade  30  can reside in the non-working transit orientation shown in  FIG. 3 ; 
       FIG. 3  is a partial side elevation of the self-adjusting snow plow  10  shown in  FIGS. 1 and 2 , but showing the plow blade  30  in the non-working, transit orientation; 
       FIG. 4  is a front elevation of an alternate self-adjusting snow plow  10 ′; the plow blade  30 ′ is shown in a working orientation and is shown in phantom in further working orientations when one end or the other is raised with respect to the mounting uprights  20 ′; 
       FIG. 5  is a top elevation of the self-adjusting snow plow  10 ′ shown in  FIG. 4 ; 
       FIG. 6  is a top elevation of a further alternate embodiment of the self-adjusting snow plow of the present invention showing a plow blade  30 ″ in phantom which is the same as that shown in  FIG. 5 , but showing an alternate mounting apparatus  14 ″ having a pivotal hitch assembly  42  which can be secured to place the plow blade  30 ″ at an angle to a plane perpendicular to a line parallel to a forward direction of the vehicle (not shown); 
       FIG. 7  is an exploded perspective view of the self-adjusting snow plow  10  shown in  FIGS. 1-3 ; 
       FIG. 8  is a cross-sectional side view of the plow blade  30  shown in  FIG. 7  as seen from the line  8 - 8  of  FIG. 7 ; 
       FIG. 9  is a side elevation of the alternate self-adjusting snow plow  10 ′ shown in  FIGS. 4 and 5  illustrating how the plow blade  30 ′ slides upwardly with respect to the mounting uprights  20 ′ when it moves forward and comes into contact with a relatively immovable object on the ground  56 , wherein the drawing illustrates in phantom the plow blade  30 ′ in a working orientation as it is moving forward toward such a relatively immovable object and also showing the plow blade once it has moved upward with respect to the mounting uprights  20 ′ after the rubber scraper  36 ′ has come into contact with such a relatively immovable object; 
       FIG. 10  is a side elevation of the alternate embodiment of the self-adjusting snow plow  10 ′ shown in  FIGS. 4-5  and  9  showing how the bottom of the plow blade  30 ′ pivots outward away from the mounting uprights  20 ′ when the vehicle (not shown), to which the self-adjusting snow plow  10 ′ is attached, moves backward drawing the plow blade  30 ′ with the vehicle; 
       FIG. 11  is a side elevation similar to that shown in  FIG. 10 , but showing the plow blade  30  shown in  FIGS. 1-3  when the vehicle (not shown) moves backward drawing the preferred plow blade  30  with it in a manner which allows the bottom of the plow blade  30  to pivot forward, away from the mounting uprights  20 ; 
       FIG. 12  is a partial side elevation of an alternate plow blade  30 ″ having an alternate rubber scraper  36 ″; 
       FIG. 13  is a further partial side elevation of an alternate plow blade  30 ′″ showing a further alternate rubber scraper  36 ′″; 
       FIG. 14  is a side elevation of a portion of a further alternate embodiment of the present self-adjusting snow plow  10 ″″ showing an alternate catch structure at the upper end of the mounting upright  20 ″″ which also includes an alternate attachment member including a removable pin  80  with which to secure the retention member  38 ″″ within the attachment member  51 ″″; 
       FIGS. 15 and 16  are top plan views of alternate retention members  84 ,  84 ; 
       FIG. 17  is a side elevation of the alternate retention member  84 ′ shown in  FIG. 16 ; 
       FIG. 18  is a top plan view elevation of a further alternate retention member  84 ″, which is pivotally secured to the alternate plow blade  30 ′″″″; 
       FIG. 19  is a side elevation of the alternate retention member  84 ″ shown in  FIG. 18 ; 
       FIG. 20  is a front elevation of an alternate self-adjusting snow plow  110 ; similar to that shown in  FIG. 4  where the plow blade  30 ′ is shown in a working orientation and is shown in phantom in further working orientations when one end or the other is raised with respect to the mounting uprights  20 ′, but the plow blade  130  includes alternate first and second retention members  138 , each of which just partially encircles one of the respective mounting uprights  120 ; 
       FIG. 21  is a front elevation of an alternate self-adjusting snow plow  110 ′; similar to that shown in  FIG. 4  where the plow blade  130 ′ is shown in a working orientation and is shown in phantom in further working orientations when one end or the other is raised with respect to the mounting uprights  120 ′, but the plow blade  130 ′ includes further alternate first and second retention members  138 ′, each of which just partially encircles one of the respective mounting uprights  120 ′; 
       FIG. 22  is a front elevation of an alternate self-adjusting snow plow  110 ″; similar to that shown in  FIG. 4  where the plow blade  130 ″ is shown in a working orientation and is shown in phantom in further working orientations when one end or the other is raised with respect to the mounting uprights, but the plow blade only includes a single retention member  238  which encircles both of the mounting uprights; 
       FIG. 23  is a front elevation of an alternate self-adjusting snow plow  110 ′″; similar to that shown in  FIGS. 4 and 22  where the plow blade  130 ′″ is shown in a working orientation and is shown in phantom in further working orientations when one end or the other is raised with respect to the mounting uprights  120 ′″, but the plow blade  130 ′″ includes an alternate retention member  238 ′, which just partially encircles each of the mounting uprights  120 ′″; 
       FIG. 24  is an exploded perspective view, similar to that shown in  FIG. 7 , but showing a new embodiment of the snow plow  310  of the present invention having an extruded aluminum mold board  332  having attachment channels  301 ,  302 ; and showing another alternate mounting apparatus  314  having a pivotal swivel apparatus  311  for pivoting the mounting frame  309  with respect to the direction of travel of the vehicle (not shown) in a manner somewhat similar to the manner in which the alternate mounting apparatus  14 ″, shown in part in  FIG. 6 , functions, but in a different way; and also providing alternate mounting uprights  320  having alternate attachment members  351 , and also showing engagement apparatus (e.g. retention hook  341 ) for engaging to the plow blade  330 , a resilient elongated member  391 , secured to the alternate mounting apparatus  314  when the plow blade  330  is in a working orientation for use during snow plowing operations; 
       FIG. 25A  is a cross-sectional side view of the alternate plow blade  330  of the improved snow plow  310  shown in  FIG. 24 , as seen from the line  25 - 25  in a manner similar to that shown in  FIG. 8  for the embodiment shown in  FIG. 7 ; 
       FIG. 25B  is a cross-sectional side view just like that shown in  FIG. 25A , except that only the mold board  332  is shown and all the other parts of the plow blade  320  shown in  FIG. 25A  have been removed to show the attachment channels; 
       FIG. 25C  is a view similar to that shown in  FIG. 25A , but showing only a portion of the plow blade  330  that is changed to shorten the metal plate  339 ′ to which the retention member is welded and to provide a counter-sunk screw  303 ′ that secures into the nut  304 ′ in the attachment channel  302 , rather than a bolt and washer as shown in the embodiment shown in  FIG. 25A ; 
       FIG. 26  is a perspective view of a portion of the alternate snow plow  310  shown in  FIG. 24 , but from a different perspective than that of  FIG. 24 ; one that is slightly less elevated and from about 180 degrees from the view shown in  FIG. 24  in a horizontal plane, and showing a retention member  338  of the alternate plow blade  330  engaged in the mounting upright  320  of the alternate mounting apparatus and also showing an additional securing pin  383  in phantom, in an orientation in which it would have to reside in order to be either inserted or removed from an alternate securing pin slot  385   a  of the alternate attachment member  351  shown in this Figure; 
       FIG. 27  is a partial side elevational view of elements of the alternate snow plow  310  shown in  FIG. 24 , that are shown in  FIG. 26 , with the exception that the securing pin  383  is removed and the retention member  338  is shown in phantom in a transitional orientation in which the retention member  338  would occasionally pass through when the plow blade  330  is either placed in or removed from a resting, non-operational, or transit position, and the retention member  338  is either placed in or removed from the attachment member  351 , before or after being in a working or operational position similar to that shown in  FIGS. 1 and 9 ; 
       FIG. 28  is a partial side elevational view similar to  FIG. 27 , but showing the securing pin  383  in an engaged position in the attachment member  351  of the alternate mounting upright  320  and the retention member  338  in solid line, but showing movement of the retention member  338  in phantom to a raised position; 
       FIG. 29  is a partial perspective view of a further alternate mounting upright  320 ′, shown in a manner similar to that shown in  FIG. 26 , but showing yet another embodiment of the mounting upright  320 ′ having an attachment member  351 ′ cut into the upper portion of the mounting upright  320 ′, and showing the securing pin  383 , in a partial exploded view, out of the securing pin receiving slot  385   a ′ in an orientation that will permit it to be inserted in the slot  385   a′;    
       FIG. 30  is a side elevational view, similar to that shown in  FIG. 27 , but showing the alternate mounting upright  320 ′ and attachment member  351 ′ shown in  FIG. 29 , and showing the securing pin  383  in the receiving slot  385   a ′, with additional retention members  338  shown in phantom to demonstrate how the securing pin  383  can limit the upward movement of the retention member  338  along the mounting upright when the retention member  338  is slideably secured on the mounting upright  320 ′ and is not within the attachment member  351 ′; 
       FIG. 31  is a front elevational view taken from line  31 - 31  of  FIG. 30 , showing a cross-section of the securing pin  383  and showing the pin  383  in place in the receiving slot  385   a ′ as shown in  FIG. 30 , and showing the handle  383   b  of the securing pin  383  in hidden line, behind the upper portion of the mounting upright  320 ′, pointing in a downward, resting position; 
       FIG. 32  is a view similar to that shown in  FIG. 31 , but showing the handle  383   b  of the securing pin  383  in an upright position, or orientation, in which it must reside in order to be effectively inserted or removed from the pin receiving slot  385   a ′ of the alternate attachment member in the upper portion of the alternate mounting upright; 
       FIG. 33  is a perspective view of an optional angle interceptor  311  including a pivoting swivel mechanism in the vehicle connection member  323  of the alternate mounting apparatus  314  shown in  FIG. 24 ; 
       FIG. 34  is a partially broken away side elevational view of the pivoting swivel mechanism of the optional angle interceptor  311  shown in  FIGS. 24 and 33 , but showing the side of the pivoting swivel mechanism partially broken away to show the upper and lower structural plates  312   a ,  312   b  through which the pivot bolt  377  and the positioning pin  321  pass to orient the mounting frame  309 ; and showing a channel for the mounting uprights  320  in phantom; 
       FIG. 35  is a top plan view of the pivoting swivel mechanism of the vehicle connection member  323  shown in  FIG. 33  showing the interconnection member  322  of the mounting frame  309  (shown in phantom) in a generally perpendicular orientation with respect to the direction of travel of the vehicle (not shown) to which the mounting apparatus  314  would be interconnected, with the exception that the angle setting pin  321  is shown in cross-section; 
       FIG. 36  is a top plan view similar to that shown in  FIG. 35 , but showing the mounting frame  309  (shown in phantom) turned to the right from the perpendicular orientation shown in  FIG. 35 ; 
       FIG. 37  is a top plan view similar to that shown in  FIG. 35 , but showing the mounting frame  309  (shown in phantom) turned to the left with respect to the perpendicular orientation shown in  FIG. 35 ; 
       FIG. 38  is a diagrammatic view of the alternate mounting frame  309  shown in  FIG. 24  as seen from the front of the vehicle (not shown) to which the mounting apparatus  314  preferably would be secured, when the mounting frame  309  is in a perpendicular orientation as shown in  FIG. 35 , and showing the plow blade  330  in a raised position, and the preferred resilient elongated member  391  attached only to the mounting frame  309  and showing the plow blade  330  in a working or an operation orientation in phantom; 
       FIG. 39  is a diagrammatic view similar to that shown in  FIG. 38 , except that the plow blade  330  is in a lowered working orientation, wherein the retention members  338  are disengageably secured to the mounting uprights  320  for snow plowing operations; and the resilient elongated member  391  is interconnected between the mounting frame and the plow blade  330  creating downward force of the plow blade  330 ; 
       FIG. 40  is a diagrammatic view similar to that shown in  FIG. 38 , except that one end of the plow blade  330  is disengaged from the attachment member  351  and is disengageably secured to the mounting upright  320  and resting on the ground  56 , and the plow blade  330  is shown in phantom in the non-working or transit orientation; 
       FIG. 41A  is a cross sectional view of an upper portion of the plow blade  330  shown in  FIG. 24  as seen from the line  41 - 41 , but showing an alternate attachment hook  341  secured in the upper attachment channel  301  of the alternate plow blade  320  shown in  FIG. 24 ; 
       FIG. 41B  is a view similar to that shown in  FIG. 41A , except that a further alternate attachment hook  341 ′ is shown; 
       FIG. 42  is a perspective view of an alternate hook apparatus  341 ″ secured to a mold board  332  similar to that shown in  FIG. 24 ; 
       FIG. 43  is a perspective view similar to  FIG. 42 , but showing a further alternate hook apparatus  41  fastened to a mold board  32  similar to that shown in  FIG. 7  and showing the screws  4  used to secure one of the two alternate attachment hooks  41  exploded away from the mold board  32  on one side; 
       FIG. 44  is a diagrammatic view of the alternate mounting frame shown in  FIG. 4 , similar to that shown in  FIG. 38 , except that alternate attachment hooks  341 , like that shown in  FIG. 41B , are secured in the upper attachment channel  301  of the alternate plow blade  330  and the resilient elongated member  391  is attached to three-quarter turn eyebolts  396  secured to the inside of a bottom portion of the respective mounting uprights  320 ; 
       FIG. 45  is an enlargement  45 - 45  of the respective three-quarter turn eyebolts  396  secured to the respective mounting uprights  320 , to which the resilient elongated member  391  is attached; 
       FIG. 46  is a diagrammatic view similar to that shown in  FIG. 39 , except that the three-quarter turn eyebolts  396  shown in  FIGS. 44 and 45  are used to engage the resilient elongated member  391  to the mounting frame  320  and the resilient elongated member  391  is engaged to the alternate attachment hooks  341 ′ shown in  FIGS. 41B and 44 ; 
       FIGS. 47 and 48  are front elevations of an alternate mounting apparatus  414  (which is partially broken away in  FIG. 47 ) of the present invention shown with alternate plow blades  430 ,  430 ′ that are partially shown, except that alternate retention members  438  and  438 ′ that are shown partially in phantom, as are parts of the mounting apparatus  414 ; 
       FIG. 49  is a cross-sectional view of the plow blade  530  similar to that of  FIG. 8  except that in this embodiment, the mold board  532  includes first and second pieces  532   a ,  532   b;    
       FIG. 50  is a partial, cross-sectional, exploded side elevational view of first and second pieces  532   a  and  532   b  of the mold board  532  shown in  FIG. 49 ; 
       FIG. 51  is a partial, exploded view of the scraper holding channel  534  and rubber scraper  536  of  FIG. 49  depicting a possible configuration wherein the scraper mates with the scraper holding channel; 
       FIG. 52  is a cross-sectional side elevational view of a further preferred embodiment of the plow blade  630 , having similarities to the plow blade shown in  FIG. 8 , but having only support members  610 ,  611  having surfaces that engage the front  666  of the mold board  632  from the back when pushing against metal plates  639  (one of which is shown in phantom); 
       FIG. 53  is a partial, perspective view of an alternate embodiment of the top of a mounting upright  720  and a corresponding pin (shown in phantom); 
       FIG. 54  is a partially broken away, partial side elevated view of the mounting upright  720  of  FIG. 53 ; 
       FIG. 55  is a partial perspective view of a preferred rubber scraper  736  having a skid bracket  780  that protects a rear edge  737  of the bottom of the rubber scraper when the rubber scraper is pulled backwards as shown in  FIG. 56B ; 
       FIG. 56A  is a side view, which shows the rubber scraper  736  of  FIG. 55  in use within a mold board  632  similar to that shown in  FIGS. 49 ,  51  and  52  and showing the rubber scraper  736  slightly flexed as it would be as it moves forward along a ground surface  56  to push snow (not shown) or the like; 
       FIG. 56B  is a side view of the preferred rubber scraper  736  within the mold board  632  shown in  FIG. 56A , but showing the rubber scraper lying somewhat flat and being flexed forward somewhat as it would be when the mold board  632  and the rubber scraper  736  are pulled backward along the ground surface  56 , showing that the skid brackets  780  elevate the rear edge  737  of the bottom of the preferred rubber scraper  736  and, thereby, protect the rear edge  737  from wear when pulled along the ground surface  56 ; 
       FIG. 57  is a partial, rear perspective view of the plow blade  630  of  FIG. 52  as it may be used in conjunction with the scraper blade  736  of  FIGS. 55-57 ; 
       FIG. 58  is a partial, rear perspective view of the plow blade having retention members  638  and a multi-function elongated member  800  used to connect the plow blade to a mounting apparatus in a first operational mode; 
       FIG. 59  is a partial, rear elevational view of the plow blade, retention members, and the multi-functional elongated member  800  of  FIG. 58 ; 
       FIG. 60  is a partial, rear perspective view of the plow blade having retention members  638  and a multi-function elongated member  800  used to connect the plow blade to a mounting apparatus in a second operational mode; and, 
       FIG. 61  is a partial, rear elevational view of the plow blade, retention members, and the multi-functional elongated member  800  of  FIG. 60 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the drawings, and more particularly, to  FIGS. 1-3 , an alternate embodiment of a self-adjusting snow plow  10  of the present invention is shown. The preferred snow plow  10  includes a mounting apparatus  14  and a plow blade  30 . The mounting apparatus  14  of this embodiment includes two mounting uprights  20  that are interconnected by an interconnecting member  22 . In this embodiment, a hitch tongue  24  is secured to the interconnecting member  22 . The hitch tongue  24  is secured to the interconnecting member  22  with a resilient connecting member  27  located between the interconnecting member  22  and a flat connecting plate  28  of the hitch tongue  24 . A hitch tongue securing pin  29  secures the hitch tongue  24  in a hitch receiver  16 , which is secured to a vehicle  18  (partially shown in phantom in  FIG. 1 ). The resilient connecting member  27  operates in a manner similar to a motor mount and allows the entire snow plow  10  some flexibility when the plow blade  30  is subjected to heavy load forces. Moreover, the connecting member  27  is believed to reduce the shock and vibration in the vehicle  18  due to impacts against relatively immovable objects. The connecting plate  28  is bolted to the interconnecting member  22  by a series of fasteners, preferably bolts  25  secured by nuts  26 . 
   Referring now also to  FIGS. 7-8  and  11 , a preferred plow blade  30  includes a mold board  32  providing a scraper holding channel  34  in which a scraper  36  is secured. In this embodiment, the mold board  32  is a single piece aluminum extrusion, although other materials may be used. The plow blade  30  also includes two retention members  38  and a plurality of lifting handles  40 . The plow blade  30  has enlarged end caps  46  secured at each end of the plow blade  30  with fastening elements  49  that extend through blade cap securing plates  48  and into constricted channels  67 . In preferred embodiments, the end caps  46  and the rubber scraper  36  are made of resilient elastomeric materials such as hardened natural rubbers and other synthetic materials, which have been used commercially to replace such products. In preferred embodiments, this elastomeric material will be an elastomer such as Styrene-Butadiene Rubbers (SBR), butylene rubbers (copolymers of isobutylene and isoprene), Acrylonitrile-Butadiene rubbers (NBR), neoprene, Thiokol® rubbers or the like; preferably SBR. In the most preferred embodiments 60 Durometer SBR is used. It will be appreciated that the term “rubber”, when used to describe the various embodiments of the scraper  36  or the end cap  46 , is used in a general sense and is not meant to limit the material used to construct the scraper  36  or the end cap  46  solely to rubber, but that it will also mean the aforementioned elastomers and other like materials. 
   Referring now also to  FIGS. 4-5  and  9 - 10 , a further alternate embodiment of the plow blade  30 ′ is shown in which the end caps  46 ′ are metal sheets the size of and similar to the blade cap securing plates  48  of the embodiment shown in  FIGS. 1-3  and  7 - 8 . These end caps  46 ′ do not extend beyond a bottom  60 ′ of the mold board  32 ′. It will be appreciated that the embodiment shown in  FIGS. 1-3 ,  7  and  11  can be modified by removing the end caps  46  and simply replacing them with the end cap securing plates  48 , which take the place of and become the replacements for the end caps  46 , as used in the alternate embodiments shown in  FIGS. 4-5  and  9 - 10 . With the exception of the respective different end caps  46  and  46 ′, everything else about these embodiments is generally the same. 
   Referring now also to  FIG. 6 , a further alternate mounting apparatus  14 ″ is shown in which the mounting uprights  20 ″ are secured to an interconnecting member  22 ″ which is joined to a pair of generally identically shaped, upper and lower parallel plates  42 , only one of which is shown, which sandwich and are pivotally connected with an alternate hitch tongue  24 ″ by a pivot pin  77 . A removable lock pin  21  is used to secure the plates  42  in one of several positions (as shown in phantom) by removing the lock pin  21  and turning the blade  30 ″ so that holes  78  (shown only in the upper plate shown in  FIG. 6 ) in the respective plates  42  are brought into alignment with a hole in the hitch tongue (not shown). 
   The plow blade  30 ′ of the second embodiment shown in  FIGS. 4-5  and  9 - 10  has been found to be somewhat more effective than the first embodiment of the plow blade  30  (shown in  FIGS. 1-3 ,  7  and  11 ), when the plow is pivoted in either direction to push snow to one side or the other of the vehicle  18 , because the larger end caps  46  of the first embodiment are not used. This makes it easier for snow to slide off of one end of the plow blade  30 ′,  30 ″ or the other when the plow blade is being pushed forward. It is possible to address this potential enhancement by simply removing the end cap  46  from one end of the preferred plow blade  30 , when it is used with the alternate mounting apparatus  14 ″, in which case the end cap  46  at the end which is tilted backwards will be the one which is removed and replaced by the end cap securing plate  48  to permit snow to easily slough off of or away from that end of the plow blade  30 , rather than collect snow, which may make plowing operations more difficult. 
   In  FIG. 1 , the preferred plow blade  30  is shown in a working orientation in which the retention members  38  encircle the respective mounting uprights  20 . As the snow plow  10  is pushed forward and force is applied to the plow blade  30  and the rubber scraper  36 , the rubber scraper has a tendency to bend backward due to frictional forces exerted at its lowermost edge, furthest removed from the mold board  32 . As shown, the rubber scraper will generally bend at a deflection or pivot point  81  located about half way between the end of the plow blade  30  and the surface being plowed. As will be appreciated, the tendency of the rubber scraper is to return to its undeflected state. In this way, the rubber scraper  36  can have a lifting effect on the plow blade  30 , forcing the plow blade and retention member  38  to slide upward along the mounting uprights  20  in a constrained manner until the retention member  38  strikes a catch structure  50  at an upper end  52  of the mounting uprights  20  as shown in phantom in  FIG. 1 . In alternate embodiments shown elsewhere (see  FIGS. 14 ,  26 - 28  and  29 - 30 ), the upward movement of the retention member  38  relative to the mounting upright is restricted by a retention pin ( 80  in  FIGS. 14 and 82  in  FIGS. 26-28  and  29 - 30 ), which will limit the upward movement of the retention members  38 , so long as the pin or pins are engaged in the respective attachment members  51 ″″,  351  and  351 ′. 
   Referring now also to  FIG. 9 , which shows the alternate embodiment shown in  FIGS. 4 and 5 , it is noted that the retention member  38 ′ will also slide upward in a constrained manner when the rubber scraper  36 ′ comes into contact with a relatively immovable object  54  along the ground  56  such as a curb or the like. As shown in  FIG. 1 , the rubber scraper  36  will also bend backwards at its lowermost edge when it is pushing a mass of accumulated snow  58 . 
   Referring now also to  FIG. 10 , when the vehicle  18  (not shown) is placed in reverse and the plow blade  30 ′ is drawn backwards, the bottom  60 ′ of the plow blade  30 ′ will naturally pivot away from the mounting uprights  20 ′ because the plow blade  30 ′ is only secured at the top  62 ′ by the retention members  38 ′ which act, in essence, as slidable hinges upon which the plow blades  30 ,  30 ′ (etc.) of the present invention can move along the length of the mounting uprights, and which can pivot to a limited degree in such circumstance. 
   Referring now also to  FIGS. 8 and 11 , in which the first embodiments of the adjustable snow plow  10  and the plow blade  30  are shown, when a vehicle (not shown) goes into reverse and the plow blade  30  is dragged backwards, the retention members  38  allow the plow blade  30  to slide downwardly along the mounting uprights  20 . When this occurs, an angle a 2  is formed between the plane  29  of the uprights and the plane  64  of the main surface of the plow blade  30 . As the angle a 2  increases, the rubber scraper  36  is raised above the ground  56  because the end caps  46  extend well beyond the bottom  60  of the mold board  32  and the scraper holding channel  34  provided by the mold board  32  for the rubber scraper  36 ; this permits snow and gravel and debris to pass below the rubber scraper  36  when the plow blade  30  is dragged backwards. This is advantageous in certain situations where there is a desire not to draw snow backwards with the plow blade  30 . When using other devices, it is often necessary to lift the plow blade  30  so as to not draw snow  58  backwards when taking the vehicle in reverse. In this case, however, the extension to the plow blade  30  provided by the end caps  46  raises the bottom of the mold board  32  and the rubber scraper  36 , which extends away from the mold board  32  at an angle. Referring now also to  FIG. 8 , this angle, angle a 1 , relative to a plane  64  of the main surface  66  (shown in phantom in  FIG. 11 ) of the plow blade  30  is at least about 10°, preferably at least about 20°, more preferably at least about 25°, even more preferably at least about 30°, even more preferably at least about 32° and most preferably at least about 32.5°. In preferred embodiments, the end caps  46  extend below the mold board  32  a distance d 3 . In preferred embodiments, this distance is at least about 2.0 inches, preferably at least about 2.5 inches, more preferably at least about 3.0 inches, and most preferably at least about 3.5 inches, and even more preferably at least about 4.0 inches. 
   In preferred embodiments, the rubber scraper  36 ,  36 ′ is skirtboard rubber which has a thickness, d 1 , in a range from about 0.5 to about 2.0 inches, preferably about 0.625 to about 1.75 inches and more preferably from about 0.75 inches to about 1.5 inches. In the most preferred embodiments, the thickness of the rubber scraper  36 ,  36 ′ is about 1.0 inch and it is made of SBR rubber having a durometer hardness of about 60, although it may be more or less than 60 depending on the nature of the climate of the environment in which it will be used and other considerations, including wear resistance, speed of use and the like. The length of the rubber scraper  36 ,  36 ′, designated by line d 4 , is preferably in a range from about 4.0 to about 10.0 inches, more preferably from about 5.0 to about 9.0 inches, even more preferably from about 6.0 to about 8.0 inches. In the most preferred embodiments, the length of the rubber scraper  36 ,  36 ′ will be about 6.5 inches. In preferred embodiments, the length, d 2 , of the amount of the rubber scraper  36 ,  36 ′ which extends beyond the end of the scraper channel  34  of the mold board  32 ,  32 ′ is preferably from about 3.0 to about 7.0 inches, more preferably from about 4.0 to about 6.0 inches, most preferably about 5.0 inches. In preferred embodiments, the length of the rubber scraper  36 ,  36 ′ which extends beyond the end of the scraper channel  34  of the mold board  32 ,  32 ′ is at least about 2.5 inches, preferably at least about 3.0 inches, more preferably, at least about 3.5 inches, even more preferably at least about 4.0 inches, and even more preferably, at least about 4.5 inches, most preferably at least about 5.0 inches. 
   Referring now also to  FIG. 12 , a further embodiment of the rubber scraper  36 ″ is shown. In this embodiment, the rubber scraper  36 ″ is made up of two separate sheets of skirtboard rubber whose top edges are secured to the scraper channel  34 ′ of mold board  32 ″ in a side by side relation. 
   Referring now also to  FIG. 13 , a further alternate embodiment of the rubber scraper  36 ′″ is shown in which the rear surface of the rubber scraper  36 ′″ includes a slight bevel  68  or chamfer at the lower end or bottom edge  70  of the rubber scraper  36 ′″. 
   Referring now again specifically to the first embodiments shown in  FIGS. 2 and 3 , the plow blade  30  may be moved from a working orientation, similar to that shown in  FIG. 1 , to a non-working transit orientation or position shown in  FIG. 3  by raising one end of the plow blade  30  to the upper end  52  of the mounting upright  20 , swinging the bottom  60  of the plow blade  30  outward and away from the mounting upright  20  to permit the retention member  38  to slide back past and over the catch structure  50 , and then down into the attachment member  51  where it can be retained as shown in  FIG. 3 . After this has been done at one end, the same process can be followed to lift the retention member  38  of the opposite end of the plow blade  30  off of the mounting upright  20  so that the retention member  38  can be placed in the attachment member  51  in a manner similar to that shown in  FIG. 3 . Once both retention members  38  are retained within the respective attachment members  51  at the upper ends  52  of each of the mounting uprights  20 , the plow blade  30  will be in a non-working, transit orientation in which the plow blade  30  is not in contact with the ground  56  and the vehicle  18  may be used for purposes other than moving accumulated snow  58  or other materials. Because of the light weight of the plow blade  30 , the plow blade  30  can be easily placed in the non-working, transit orientation by an individual. 
   It is just as easy for an individual to lower the plow blade  30  into a working or operational orientation when it is in a non-working transit orientation. To lower the plow blade  30  into a working orientation, the individual can lift a retention member  38  out of the attachment member  51  at one end, swing the bottom  60  of the plow blade  30  outward so as to generally pivot it away from the mounting upright  20 , lift the retention member  38  upwardly and rearwardly out of engagement with the attachment member  51  then lower the retention member  38  over the upper end  52  of the mounting upright  20  and allow the retention member to slide down the mounting upright  20  until the lower extremity of that end of the plow blade  30  comes into contact with the ground  56 . Once the first end is in contact with the ground, the user can lift the opposite end in a similar manner, swinging the bottom  60  of the plow blade  30  outwardly so as to pivot the bottom  60  of the plow blade  30  away from the mounting upright  20 , so that the remaining retention member  38  can be first of all disengaged from the attachment member  51  and then lowered over the upper end  52  of the mounting upright  20  until the lower extremity of the remaining end of the plow blade  30  comes into contact with the ground  56 . At this point, the plow blade  30  will be in a working orientation in which it may be pushed by the mounting apparatus to gather and remove snow or other particulate matter on the surface of the ground  56 . In alternate embodiments of the present invention shown in  FIGS. 14 ,  26 - 28  and  29 - 30 , if the retention pins  80 ,  83  are removed from the respective attachment members  51 ″″,  351  and  351 ′, it is believed to be especially easy to place the respective retention members in the respective attachment members or remove the respective retention members from the respective attachment members, because once the retention pins  80 ,  83  are removed, there is no catch member  50 , and it is a simple matter to just lift each of the respective ends of the plow blade up and either place them in the respective attachment members or remove them from the respective attachment members and, in the second case, lower that end to the ground. This is especially easy for a single person to accomplish without help from others. 
   When the plow blade  30  is lowered into the working orientation, it operates simply when the vehicle moves forward and the mounting uprights  20  push the plow blade  30  forward in a manner which will generally cause the resilient rubber scraper  36  to bend in the manner shown in  FIG. 1 . When the alternate mounting apparatus  14 ″ of  FIG. 6  is used to tilt one end of the plow blade  30 ″ back, the mounting uprights  20 ″ still push the blade  30 ″ and the retention members  38 ″ hold the blade  30 ″ in place in front of the mounting apparatus  14 ″. 
   Referring now especially to  FIG. 4 , occasionally, the plow blade  30 ′ will encounter greater resistance either to a mass of snow or other relatively immovable objects on one side or the other, causing one end of the plow blade  30 ′ or the other end of the plow blade  30 ′ to ride up on the mounting upright  20 ′ most proximate that particular end of the plow blade  30 ′, as shown in phantom in  FIG. 4 . Because the preferred retention members  38 ′ have openings  75  which are significantly larger than the mounting uprights  20 ′, the plow blade  30 ′ can ride up on one end or the other until retention member  38 ′ is stopped by the catch structure  50  at the upper end of the respective mounting upright  20  or by a retention pin  80 ,  83  as shown in other embodiments (See  FIGS. 14 ,  26 - 28  and  29 - 30 ). 
   It will be appreciated that the retention members  38 ,  38 ′ are designed and constructed to provide an opening  75  which is large enough to allow a person to lift one end of the plow blade  30 ,  30 ′ up and disengage the retention member  38 ,  38 ′ from the respective mounting upright  20 ,  20 ′ with which it is engaged when it is in a working orientation. At the same time, however, the opening  75  has been designed and constructed to disengageably secure the mold board  32 ,  32 ′ of the plow blade  30 ,  30 ′ is a manner which will not allow the retention member  38 ,  38 ′ to slide all the way to the upper end  52 ,  52 ′ of the mounting upright  20 ,  20 ′ without eventually striking the catch structure  50  or a retention pin  80 ,  83  as shown in other embodiments (See  FIGS. 14 ,  26 - 28  and  29 - 30 ), which will prevent the plow blade  30 ,  30 ′,  130  from being accidentally disengaged from the mounting uprights  20 ,  20 ′,  120 ,  120 ′. 
   Referring now also to  FIG. 14 , which shows a further alternate embodiment of the snow plow  10 ″″ in which the retention members  38 ″″ are stopped by a retention pin  80  which is secured within an alternate attachment member  51 ″″. In this embodiment, the retention pin  80  must be removed in order to lift the retention member  38 ″″ off of the upright  20 ″″ and position the retention member  38 ″″ within the attachment member  51 ″″. Once the retention member  38 ″″ is positioned within the receiving opening  82  of the attachment member  51 ″″, the retention pin  80  can be inserted through openings (not shown) in respective sides of the attachment member  51 ″″ and secured with a bale or spring wire  84 . Although not shown, a spring loaded ball bearing pin (not shown) can also be used in such an attachment member  51 ″″. In this embodiment, the function of the retaining pin  80  makes the need for a catch, such as catch  50  shown in  FIGS. 1-3 , essentially unneeded so long as the retention pin  80  is in place when the snow plow  10 ″″ is in use. 
   Referring now also to  FIGS. 15-17 , retention members  84 ,  84 ′ are shown which differ significantly from previously discussed retention members  38 ,  38 ′,  38 ″,  38 ′″ and  38 ″″ in that they are sleeve-like or collar structures that slidingly engage the mounting uprights in a telescopic, constrained manner. These retention members  84 ,  84 ′ at least partially encircle the mounting uprights  20  and  20 ′. As seen in  FIG. 15 , one retaining member  84  completely encircles the mounting upright  20  and is pivotally interconnected with the alternate mold board  32 ″″ by a securing loop  86 , which is welded to the top of the mold board  32 ″″. In  FIG. 16 , a similar retaining member  84 ′ is shown in which the retaining member  84 ′ only partially encircles the mounting upright. 
   Referring now also to  FIGS. 18 and 19 , a further embodiment of a retaining member  84 ″ is shown, which has a larger opening  75 ″, thereby giving the mounting upright  20  the ability to move not only from side to side within the opening  75 ″ but to be skewed relative to the retaining member  84 ″. Retaining member  84 ″ is pivotally attached to a securing plate  88  which is welded to the alternate mold board  32 ′″″″. It will be appreciated that the retaining member  84 ″ may also have an slotted side similar to that shown in  FIG. 16  for retaining member  84 ′. 
   Referring now also to  FIG. 20 , an alternate embodiment of the snow plow  110  is shown having alternate retention members  138  which only partially encircle the mounting uprights  120  when the plow blade  130  is in a working orientation as shown. Referring now also to  FIG. 21 , a further embodiment to the snow plow  110 ′ is shown having further alternate embodiments of the retention members  138 ′, extending in an opposite direction as compared to that shown in  FIG. 20 , but once again only partially encircling the mounting uprights  120 ′ when the plow blade  130 ′ is in a working orientation as shown. Referring now also to  FIG. 22 , a further alternate embodiment of the snow plow  110 ″ is shown in which a single retention member  238  is attached to the plow blade  130 ″. The retention member  238  is shown in a working orientation and encircles each of the respective mounting uprights  120 ″. Referring now also to  FIG. 23 , a further alternate embodiment of the plow blade  110 ′″ is shown in which a single retention member  238 ′ is attached to the plow blade  130 ′″. The retention member  238 ′ is shown in a working orientation and only partially encircles each of the respective mounting uprights  120 ′″. In each of the aforementioned alternate snow plow embodiments, the plow blade may be disengaged from the respective mounting uprights one mounting upright at a time or, as is also the case with each of the other aforementioned embodiments, the plow blades may be disengaged from the mounting uprights at the same time, if both ends of the plow blade are lifted and disengaged at the same time. 
   In the aforementioned preferred embodiments, best illustrated in  FIGS. 7 and 8 , the mold board  32  of the plow blade  30  includes a bottom  60 , a rear surface  61 , a top  62 , and a main surface  66  that define a hollow or space  69 . The hollow or space  69  of the hollow-core mold board may be provided with one or more support structures  71 ,  72 ,  73 , which extend between the main surface  66  and the rear surface  61 , and along the width of the plow blade  30 . As will be appreciated, the support structures  71 ,  72 ,  73 , which form compartments or cells within the hollow  69 , add strength to the plow blade. It will be appreciated that the mold board can be further strengthened by providing the compartments or cells with filler material such as expanded foam, without departing from the spirit and scope of the invention. Preferably the hollow-core plow blade  30  is extruded aluminum structure. In the most preferred embodiments, the aluminum surface will be clear anodized aluminum which is particularly attractive for consumers. Although the mold board can be extruded into two pieces (see  FIGS. 49 and 50 ) which are subsequently assembled, the preferred embodiment is a one-piece extrusion which saves both on cost for aluminum and on cost for assembling the mold board. In preferred embodiments, the plow blade will weigh less than about 150 pounds, preferably less than about 110 pounds. The entire snow plow  10 , including the mounting apparatus will preferably weigh about 250 pounds or less, more preferably about 225 pounds or less. 
   When force is applied to the rubber scraper  36  of the present invention, the bottom of the rubber scraper  36  will bend backwards as shown in  FIG. 1  and in  FIG. 9  in reference to the alternate embodiment of a plow blade  30 ′. The rubber scraper  36  will generally bend at a generalized deflection or pivot point  81 ′ which is located just below the lower edge of the scraper channel  34  within the mold board  32 . In softer rubber material having a durometer hardness of 40 or 50, the rubber scraper  36  tends to bend more. For that reason, harder rubber material having a durometer of at least about 60, perhaps as much as about 70 or 80, is preferred. 
   When installing the mounting apparatus  14 , it is easiest to install the mounting uprights  20  in a perfectly vertical position as this is easiest to corroborate if a carpenter&#39;s level is available for use during the installation. It is possible, however, to install the mounting apparatus so that the mounting uprights  20  are tilted either backward or forward a small amount. This will change the operational characteristics of the snow plow. When, for example, the uprights  20  are installed with a backward or negative tilt, the plow blade  30  will tend to rise somewhat more easily when it comes into contact with immovable objects, including accumulated snow  58  on the ground  56 . By contrast, when the uprights  20  are installed with a forward or positive tilt, the plow blade  30  will not rise up on the mounting uprights  20  quite as easily as it will when the mounting uprights  20  are perfectly upright. In certain situations, however, it may be desirable to tilt the uprights  20  forward about two and one-half degrees from vertical. This can cause the rubber scraper  36  to flex to a higher degree and appears to have a shock dampening effect during snow removal. Also, because the mounting uprights  20  are tilted forward, it has an added effect of keeping the plow blade  30  down when it is in use. In certain situations, this is most desirable as a user may be able to obtain superior results when the blade  30  rises somewhat less readily or when the scraper  36  comes under a lower degree of force. In this regard, it is also noted that the rubber scraper  36  should extend outwardly beyond in front of the mold board  32 . It is believed that if the rubber scraper  36  were straight up and down, the blade  30  would flex too easily and allow snow  58  to pass under the blade  30  and result in poor snow removal. It will be appreciated that the mounting apparatus can be installed with a forward or backward tilt by providing shims, which can take the form of washers or spacers that can be used with upper and lower sets of fastening elements. It is also noted that when the plow blade  30  is perpendicular to the direction of travel the rubber end caps  46  will tend to bow outwardly beyond the ends of the blade even as great as 90 degrees. This is desirable as it allows the blade to catch more snow when moving it. 
   An alternative embodiment of the mounting apparatus  14 ″ of the present invention is shown in  FIG. 6 , in which the angle of the plow blade  30 ″ can be varied in relation to its direction of travel. This embodiment features a pivotally mounted snow plow  79  and allows the user to discharge snow to either side of the plow vehicle. In this embodiment of the invention, the connection of the hitch tongue  24 ″ to the plow blade  30 ″ is facilitated through the use of a pivot plate  42  and a pivot pin  77 . The pivot plate  42  which is fastened to the interconnecting member  22 ″ includes an aperture  76  that is configured to receive a pivot pin  77 . The pivot pin  77  also passes through a first aperture at the end of hitch tongue  24 ″, which is connected to a vehicle (not shown). As will be understood, the pivot pin  77  enables the pivot plate  42  and its attendant plow blade  79  to rotate or swivel in a generally horizontal plane relative to the hitch tongue  24 ″ and its attendant vehicle. 
   Additionally, the pivot plate  42  and the hitch tongue  24 ″ are equipped with a plurality of alternate holes or apertures, which, when used in conjunction with a locking pin  21 , are used to lock the pivoting plow  79  into positions that push snow straight ahead, as shown in  FIG. 6 , or to the left or the right as shown in phantom in  FIG. 6 . In particular, pivot plate  42  includes holes  78  that are configured to receive the lock pin  21 , and the hitch tongue  24 ″ includes a second aperture that is configured to receive lock pin  21 . In operation the plow blade  30  is rotated about pivot pin  77  until the holes in the pivot plate are aligned with the second aperture in the hitch tongue  24 ″. Once the alignment is achieved, the lock pin  21  is inserted through both the holes and the aperture. This allows the user to employ this embodiment of the present invention in a plurality of orientations. The first of these is to lock the pivoting plow  79  in the position in which the plow blade  30 ″ is generally perpendicular or square in relation to the line of travel. Conversely, to employ the side discharge function, the user simply locks the pin  21  in the desired alternate locking holes  78  to discharge the snow on a desired side of the vehicle (not shown) pushing the snow plow. It will be appreciated that the lock pin  21  need not engage the second aperture in the hitch tongue  24 ″ in order for the plow blade to be secured. The plow blade  79  could also be secured by two lock pins or a U-shaped lock bar whose arms are received by holes  78  and which engage the outer surfaces of the hitch tongue  24 ″. In addition, it will also be appreciated that the plow blade  79  can be secured at angled positions by one lock pin  21  and a portion of the pivot plate structure. In this instance, the lock pin  21  and the pivot plate structure would engage the outer surfaces of the hitch tongue  24 ″. 
   Referring now also to  FIGS. 24 ,  25 A,  25 B, and  26 - 28 , a commercial embodiment of the self-adjusting snow plow  310  is shown. The self-adjusting snow plow  310  includes a mounting apparatus  314  having a transition apparatus  323  that is attachable to a mounting frame  309 . The transition apparatus  323  includes a hitch tongue  324  which can be received by a hitch receiver  316  (shown in phantom) that is attached to the front of a vehicle (not shown) in a manner similar to that disclosed in relation to the embodiment shown in  FIGS. 1 and 7 . The transition apparatus  323  also includes a bell-shaped housing or subframe  311 , which will be further described below. The bell-shaped housing or subframe  311  is movably interconnected to the hitch tongue  324  by an extension  308  that is pivotally connected to the bell-shaped housing or subframe  311  by a pivot pin  377  in a manner similar to pivot pin connection of  FIG. 6 , discussed previously. The housing or subframe  311  includes a plate  328  that is secured to the interconnecting member  322  of the mounting frame  309  by a series of bolts  325  secured by a series of nuts  326 . The mounting frame  309  includes a pair of mounting uprights  320 , preferably 33 inches apart on center, connected by the interconnecting member  322 . 
   The plow blade  330  includes a mold board  332  having upper and lower attachment channels  301 ,  302 , respectively, in which a variety of parts or elements, described below, can be secured or anchored. As shown, the channels have constricted portions and enlarged portions and are configured to be used with conventional fastening elements having elongated bodies terminating with enlarged heads, preferably by a series of complimentary fastening elements, such as, for example, threaded bolts  303  received by a series of reciprocally threaded nuts  304 , preferably square or hex-headed nuts. As will be appreciated the channels are sized to slidingly receive the enlarged portions of the fastening elements and include oppositely facing flanges that form a constriction or slot. In addition, the channels are preferably sized so that the flats of the enlarged heads contact the side walls  401  and  402 ,  403  and  404  of channels  301  and  302 , respectively, and the fastening element is prevented from axial rotation. Alternatively, a square or hex head of a threaded bolt can be secured in the channel and the nuts can be used to secure the respective parts to the bolt. In this regard, it will be appreciated that while threaded bolts and reciprocally threaded nuts are preferred, other fastening mechanisms known in the art may be used to secure the various parts of the present invention to the plow blade. 
   The plow blade  330  also includes end caps  346  and end plates  348  similar to those described in relation to the embodiments disclosed in relation to  FIGS. 1-3 ,  7 - 8  and  11 . In addition, a pair of guide shafts  387  are secured to the respective ends of the mold board  332 , preferably with a pair of fasteners, one of which is normally used to secure the end plate  348  and the end cap  346  in a constricted channel  349  in the extruded aluminum mold board (see  FIGS. 25A and 25B ), which also illustrate a preferred rubber scraper  336  similar to those disclosed in relation to the first embodiment of the present invention disclosed in FIGS.  1  and  7 - 8 , as well as the scraper channel  334  in the mold board  332  in which the rubber scraper  336  is secured. 
   Although a two piece or multiple piece aluminum extrusion can be used to form the mold board  332 , (see for example  FIGS. 49 and 50 ) a single piece aluminum extrusion may be more efficient and provide a more cost effective structure in so far as no assembly is required. On the other hand, a two piece construction may be more efficient and cost effective in so far as it can use smaller, less expensive dies that can be integrated into more manufacturing facilities. The mold board  332 , shown without any attachments in  FIG. 25B , is the most preferred embodiment of the mold board. It comprises a bottom  331 , a mold board or main surface  332 , a top  333 , and a rear surface  335 . It also includes a series of internal support structures  353 ,  354 ,  355  that strengthen the mold board  332  by extending between and connecting the rear wall  335  and the main surface of the mold board  332 , just as the internally reinforcing support structures in the earlier embodiments strengthen the mold board  32  of  FIG. 8 , which has been previously disclosed. In general, with regard to the support structures of the previously discussed embodiments, the support structures are shown as being parallel to each other. However, this need not be the case in order to practice the invention. For example, the support structures may be angled relative to each other. 
   The plow blade  330  disclosed in  FIGS. 24 ,  25 A,  25 B and  26 - 28  includes two lifting handles  340  on opposite ends of the mold board  332 , anchored in the upper attachment channel  301 , two retention hooks  341 , also secured in the upper attachment channel, but placed closer to the middle of the mold board  332 , and two retention apparatus assemblies  337 , each including a retention member  338  welded to a retention plate  339  that is anchored to the mold board by fastening elements such as threaded bolts  303  secured to reciprocally threaded nuts  304 . As shown, the threaded nuts  304  are received in attachment channels  301  and  302 , and serve as attachment points for threaded bolts  303 . It will be appreciated, however, that the positions of the nuts and bolts may be reversed, if so desired, without departing from the spirit and scope of the invention. 
   In preferred embodiments, the snow plow apparatus  310  can be provided with a mechanism or a device that is constructed and arranged to exert a downwardly biasing force on the plow blade  330 , when the plow blade  330  is secured to the mounting apparatus  314  in a working or operational orientation. It is believed that this downwardly biasing force will improve snow removal operations in certain circumstances that cause the plow blade  330  to ride up on the mounting uprights  320  of the mounting frame  309 . In  FIG. 24 , a preferred mechanism or device  391  is shown for exerting such a downwardly biasing force on the plow blade  330 , namely an elongated tensioning member  391 , that will be described in greater detail below. Preferably, the elongated tensioning member  391  is secured to the mounting frame  309  using fastening elements  392  such as eye-bolts or hooks. It is then stretched over the retention hooks  341  on the mold board  332  to exert the downwardly biasing force on the plow blade  330  when the plow blade is in a working orientation. It will be appreciated that other mechanisms and devices could be used to provide such a downwardly biasing force on the plow blade  330  such as, for instance, compression or tension spring elements connected between the mounting frame  309  and the mold board  332 , free weight members securable to the mold board  332 , or combinations thereof and the like. Furthermore, in alternate embodiments, it is envisioned that an alternate elongated tensioning member could be first attached or secured to the mold board and then secured to the mounting frame to place a downwardly biasing force on the plow blade. 
   Referring now also to  FIG. 25C , an alternate retention plate  339 ′ is shown in part where it differs from the alternate retention plate  339  shown in  FIGS. 24 ,  25 A and  25 B, only in that it is truncated at the bottom  331  of the mold board  332  and does not extend as far as the retention plate  339  shown in  FIG. 25A . The alternate retention plate  339 ′ is more cost effective, due in part to lowered tolerance requirements associated with fabrication because it omits the bend that would otherwise mimic the bend in the bottom  331  of the mold board. The alternate retention plate  339 ′ uses one or more counter sunk threaded bolts  303 ′ shown in  FIG. 25C  having a conical head to secure the lower portion of the retention plate  339 ′ in the lower channel  302 . 
   Referring now with particularly to  FIGS. 26-28 , the alternate mounting uprights  320  include an alternate attachment member  351  that is secured to the top  352  of each of the mounting uprights  320 . As shown in the figures, the attachment member  351  includes a base  362 , a first arm or end wall  364  and a second arm or end wall  366  and, the retention member  338  can be secured between the arms  364 ,  366  of the attachment member  351  by a retention pin  383  that is inserted through a slotted aperture  385   a  and an aperture  385   b  located in arms or end walls  364  and  366 , respectively. The retention member  338  can only be removed from the attachment member  351  if the retention pin  383  is disengaged from the attachment member so that the retention member  338  can be lifted up and over the tops of the arms. As will be understood, if the retention member  338  is lifted up and over arm or end wall  366 , that portion of the plow blade will be completely disengaged from that particular mounting upright. Whereas if the retention member is lifted up and over arm or end wall  364 , the plow blade can then be lowered into a working orientation as the retention member  338  slides down along the outer extremity of the mounting upright  320 . As shown particularly in  FIG. 28 , the retention member  338  is slidingly constrained to move freely along the exterior of the mounting upright  320 , but it is limited if the retention pin  383  is inserted in the apertures  385   a ,  385   b  of arms  364 ,  366  of the attachment member  351 . In this way, if the plow blade  330  travels upward along the mounting upright  320 , its upward travel along the mounting upright will be limited by the handle portion  383   b  of the retention pin  383  that will stop the retention member&#39;s upward travel when the retention member  338  comes into contact with the retention pin  383 . 
   Referring now also to  FIGS. 29-32 , a further alternate embodiment of the attachment member  351 ′ is shown as a cut away in the upper portion  352 ′ of a further alternate mounting upright  320 ′. The retention pin  383  can be inserted into a pair of retention slots or apertures  385   a ′ and  385   b ′ and passed through end walls of the attachment member  351 ′ so that the end  383   a  of the retention pin  383  passes through a receiving opening or apertures  385   b ′ on the opposite side of the attachment member  351 ′ in a manner that is the same as the manner in which the retention pin  383  is inserted in the previously described attachment member  351  shown in FIGS.  24  and  26 - 28 . In each case, the retention pin  383  is insertable into the retention slot  385   a ′ when the retention pin handle  383   b  is in an upright position as shown in  FIGS. 29 and 32  and in phantom in  FIG. 26 . The end  383   a  of the retention pin  383  is then passed through the retention slot or slotted aperture  385   a  and then through the receiving opening or aperture  385   b ′. It will be appreciated that the handle  383   b  of the pin  383  has sufficient weight so that it will be drawn by gravity to a downward position, 180° from the upward position shown in  FIG. 29  and  FIG. 32 . 
   As shown in  FIGS. 31 and 32 , the retaining pin  383  is able to be inserted into the retaining pin receiving slot or slotted aperture  385   a ′ when the retaining pin resides in an upright position, as shown in  FIG. 32 . In this position a securing arm  383   c  of the retaining pin  383  will pass through a slot  386  extending horizontally outward from the center of the retaining pin receiving slot or aperture  385   a ′ to accommodate passage of the securing arm  383   c  of the retaining pin  383 . Once the retaining pin  383  passes far enough into the slotted aperture  385   a ′ and the receiving opening aperture  385   b ′ so that the stop plate  383   d  of the retention pin contacts the exterior of the plate or end wall of the attachment member  351 ′, the securing arm  383   c  will be positioned within the interior of the attachment member  351  or  351 ′ with sufficient leeway to allow the handle  383   b  to turn downward under the force of gravity or otherwise so that the securing arm  383   c  will hold the retaining pin  383  within the slotted aperture  385   a ,  385   a ′ and the receiving apertures opening  385   b  and  385   b ′. Once in place, the force of gravity will maintain the handle  383   b  in a downward position so that the retaining pin  383  will be retained within the slotted aperture  385   a ,  385   a ′ and the aperture  385   b ,  385   b ′ until the handle  383   b  of the retaining pin  383  is turned upward so that the retaining pin  383  can be removed from the aperture  385   b ,  385   b ′ and the slotted aperture  385   a ,  385   a ′. Also, as noted elsewhere, the retaining pin  383  will act to limit the upward travel of the retention member  338  along the outer extremity of the mounting upright  320 ,  320 ′ when the plow blade  330  is forced to travel upward along the mounting upright. 
   Referring now also to  FIGS. 33-37 , the optional bell-shaped housing or subframe  311  is interconnected with the mounting frame pins shown in  FIG. 24  by a series of threaded bolts secured to reciprocally threaded nuts  326 , shown in  FIG. 24 ; and to the front of a vehicle in a manner similar to that shown in  FIG. 7  for the first embodiment, where a hitch tongue  24  similar to hitch tongue  324  shown in  FIG. 33  can be secured to a hitch tongue receiver  16 , similar to hitch tongue receiver  316  shown in  FIG. 24 . The transition apparatus  323  includes the hitch tongue  324  and a hitch tongue extension  308  with apertures  374 ,  375 , and which is pivotally connected at aperture  374  to the subframe  311  by pivot pin  377 . The transition apparatus  323  can pivot if the lock pin  321  is removed from engagement with the apertures  372   a  and  372   b  of subframe  311  and aperture  375  of the hitch tongue extension  308 . As shown in  FIG. 34 , the subframe  311  has an upper plate  312   a  and a lower plate  312   b . Each of the respective upper and lower plates have a pair of openings or apertures, that are vertically aligned so that, for instance, an opening  372   a  for receiving the lock pin  321  in the upper plate  312   a  is directly above and aligned with a similar opening  372   b  in the lower plate  312   b  so that the lock pin  321  can be inserted into both openings without difficulty. Furthermore, the remaining openings  370   a ,  370   b  in respective upper and lower plates  312   a ,  312   b  are also vertically aligned so that they can receive a pivot pin  377  which is preferably a threaded bolt, and which is secured below the lower plate  312   b  by a threaded nut  378 . It will be appreciated that the subframe  312  has open sides between the upper plate  312   a  and the lower plate  312   b . This design is especially helpful to permit snow, ice, water, sand and the like to escape from the area between the respective plates so that it won&#39;t interfere with the movement of the hitch tongue extension  308 , through which the pivot pin  377  extends. 
   The structure of the subframe  311  may include a drain opening  313  in the lower plate  312   b  so that, if the subframe  311  is turned upside down 180° from the orientation shown in  FIG. 33 , water, snow, ice, sand and the like which could otherwise accumulate between side walls or gussets  317   a ,  317   b  and the bottom plate  312   b  will be able to fall through the drain opening  313  to limit collection of such materials above the lower plate  312   b  that will be, in effect, the upper plate when the subframe  311  is turned upside down. It will be appreciated that the subframe can be used in either of these two orientations and that the plurality of both apertures in the flat plate  328  of the mounting apparatus  314  will facilitate placement of the subframe at various heights with respect to the mounting frame  320  so as to accommodate vehicles having hitch tongue receivers that will connect at various heights above the ground given the varying characteristics of the wide variety of vehicles to which such a hitch receiver may be attached. In this way, the plurality of apertures in the flat plate  328  allow the subframe  311  to have significant versatility for attachment of the mounting apparatus at various heights where attached in anticipation of attachment to a number of vehicles to which a hitch tongue receiver is secured. 
   It is generally believed that it is desirable to position the mounting frame  309  from about 8 to about 10 inches above the ground in order to have suitable clearance for the plow blade  330  when the plow blade  330  is engaged with the mounting uprights  320  in a working orientation. If the separation between the mounting frame  309  and the ground  56  is greater than about 10 inches the plate  328  can be disconnected from the interconnecting member  322  and rotated 180 degrees about its length, before reconnecting the plate  328  to the interconnecting member  322  to decrease separation between the mounting frame  309  and the ground  56 . If the separation needs to be increased, the bolts  325  can be disconnected from the nuts  326  and the plate  328  can be separated from the interconnecting member  322 , adjusted for height by realigning the plate  328  with the interconnecting member  322  so that the bolts  326  can secure the mounting frame  309  to the subframe  311  in a manner that allows the mounting frame to be repositioned with respect to the ground  56 . 
   It will be appreciated that the mounting frame  309  will stand generally perpendicular to the direction of movement of a vehicle when the hitch tongue extension  308  is locked in the position shown in  FIG. 35  by the lock pin  321 . Referring now especially to  FIGS. 36 and 37 , if the lock pin  321  is removed from the lock pin receiving openings in the upper plate  312   a  the hitch tongue extension  308  and the lower plate  312   b , the hitch tongue extension  308  can pivot with respect to the frame  311  through a generally horizontal plane until the hitch tongue extension  308  comes into contact with a limiter column, post or frame element  315  on either side of the aligned pin receiving openings  372   a ,  372   b  in the upper and lower plates  312   a ,  312   b . It will be appreciated from a review of  FIGS. 35-37  that the limiter columns or posts  315  allow the hitch tongue extension  308  to pivot just far enough to permit the lock pin  321  to hold the hitch tongue extension  308  in a position either to the left or the right of the aligned lock pin receiving openings  372   a ,  372   b  in the upper and lower plates  312   a ,  312   b  so that the lock pin  321  can hold the hitch tongue extension  308  in position with respect to the upper and lower plates  312   a ,  312   b  so that the mounting frame  309  can be held at an angle to the left or to the right of a position perpendicular to the forward movement of a vehicle pushing the adjustable snow plow apparatus of the present invention, so that the plow blade  320  can be held at an angle to the forward motion of the self-adjusting snow plow that is greater or less than 90° and allows snow gathered in front of the plow blade  320  to be pushed off to one side or the other of the path of a vehicle pushing the plow blade. 
   Referring now also to  FIGS. 38-39 , the present invention includes a mounting apparatus  314  (see  FIG. 24 ) having a mounting frame  309 , the mounting frame  309  including two interconnected mounting uprights  320 ; the snow plow retention apparatus  338 , preferably including at least one retention member  338 , preferably two retention members  338 , constructed and arranged to disengageably secure the plow blade  30 ,  330  to the mounting uprights  20 ,  320  for constrained motion during use; and an elongated member  390 , preferably a resilient elongated member  391  constructed and arranged to exert downward force upon the plow blade  30 ,  330  when the plow blade  30 ,  330  is disengageably secured to the mounting uprights  20 ,  320  during use and the elongated member  391  is interconnected between the plow blade  30 ,  330  and the mounting apparatus  14 ,  314 . In an alternate embodiment of the elongated member shown in  FIGS. 38 and 39 , the elongated member is a resilient shock cord  391  or bungee cord that is preferably stretched or pre-loaded to extend between two eyebolts  392  each of which is preferably secured to a bottom portion of the mounting frame  309  in the manner shown in  FIG. 38  (see also,  FIG. 24 ). The pre-loaded shock cord is capable of placing a downward force upon the plow blade  330  when the shock cord  391  is further stretched to engage retention hooks  341  secured to the mold board  332  as previously described. By stretching the shock cord  391 , which is secured to the bottom of the mounting uprights  320  in the embodiment shown in  FIG. 38 , a significant amount of downward force can be exerted upon the plow blade when it is in a working orientation as shown in  FIG. 39 . 
   Referring now also to  FIG. 41A , the retention hooks  341 , shown also in  FIGS. 24 ,  38  and  39 , are preferably made of a sheet of material (preferably steel) having a thickness of about one eighth of an inch, a length of about six to eighteen inches, and a width of from about a half an inch to about an inch and a quarter, preferably about three quarters of an inch to about an inch, most preferably about an inch wide. Referring now also to  FIGS. 41B ,  42  and  43 , further embodiments of the retention hooks  341 ′,  341 ″ and  41  are shown. The retention hook  341 ′ shown in  FIG. 41B  turns to more than 270° and leaves a relatively small opening  395  through which to pass the elongated member  391  within the retention hook  341 ′. The retention hooks  341 ″ shown in  FIG. 42  are made of one-quarter inch wire stock (preferably steel) that have been formed into a U-shape or J-shape and which have been welded to the retention apparatus assembly  337  that is secured to the mold board  332  as previously described. Referring now also to  FIG. 43 , a pair of standard hooks  41  may also be used when secured to a mold board  32  such as that shown in  FIG. 43  which is similar to that shown in  FIGS. 7 and 8 . The retention hooks  41  are secured to the mold board  32  with a pair of fastening elements such as screws  4 . 
   Referring now also to  FIGS. 44-46 , a preferred downward force generating system is disclosed in which a resilient elongated member  391  is disengageably engaged with a pair of three-quarter turn eyebolts  396  secured to a lower portion of the mounting uprights  320  and retention hooks  341 ′ such as those shown in  FIG. 40  which are attached to the plow blade  330 . In this preferred embodiment, the resilient elongated member  391  may be engaged and disengaged from the mounting uprights and the mold board through the gaps  397  and  395  the three-quarter turn eyebolts  396  and each of the three-quarter turn retention hooks  341 ′ (see  FIG. 41   b ). In this way, the elongated retention member  391  can be easily replaced and may be removed for storage when not in use. Because the climates in which snow plows are used experience significant fluctuations in temperature, having a disengageable resilient elongated member  391  is likely to increase the ability of the owner to store the elongated member  391  at moderate temperatures that are less likely to advance deterioration and increase its working life as opposed to being exposed to either high or low temperatures, which would tend to shorten its working life. As shown in  FIGS. 44-46 , the three-quarter turn eyebolts which include openings  397  similar to the openings  395  of retention hooks  341 ′ are oriented downward so that the openings  397  face away from the openings  395  of retention hooks  341 ′ when the plow blade  330  is in the working orientation shown in  FIG. 46 . This permits the rapid attachment and removal of the resilient elongated member  391  in a manner that is not disruptive of normal use of the snow plow  310 . 
   It will be appreciated that the elongated member  391  can be any resilient member that can be stretched in order to preload the elongated member so that the elongated member can exert a downward force on the plow blade  330  when the elongated member  391  is engaged with elements of the mounting apparatus  314  and elements of the plow blade  330  that are positioned with respect to each other in a manner placing the engagement elements of the mounting apparatus below the engagement elements of the plow blade when the plow blade is in a working orientation as shown in  FIG. 46 . Because the plow blade is necessarily a relatively light piece of equipment, which can be easily handled by consumers, it can ride up on the mounting uprights  320  in a manner that makes it difficult to move large amounts of snow under certain circumstances. Rather than increase the weight of the plow blade  330  to a point where it would make the plow blade more difficult for an individual to manipulate, it is believed that it is advantageous to provide a resilient elongated member  391 , such as those disclosed, that can be engaged between the mounting apparatus and the plow blade to create a downwardly biasing force on the plow blade  330  during snow plowing operations when the plow blade  330  is in a working or operational orientation. 
   It will be appreciated that any elongated member that has some elasticity and can stretch and has the ability to exert a force upon an object to which it is connected, or more particularly between two objects between which it is connected, can be used, notably materials that are used to make shock cords, bungee cords and the like. In addition, elongated members that have only a partial length or perhaps a plurality of partial lengths that are resilient may certainly be used in the place of a single long elongated member that is resilient and therefore stretchable throughout its entire length. In addition, using a plurality of elongated members, interconnected with only a single engaging element on each of the structures to be interconnected, e.g., the mounting apparatus  314  and the plow blade  330 , may also be used. In this regard, it will be appreciated that the only requirement of the engagement of the resilient elongated member or members is that they are interconnected between the mounting apparatus  314  and the plow blade  330 , when the plow blade  330  is in the working orientation. It will be appreciated that springs, rubber bands, and other resilient devices may be substituted for the preferred resilient elongated member  391  disclosed in the drawings. The preferred resilient elongated member  391  will be a shock cord having a diameter of from about an eighth of an inch to about an inch, preferably from about three eighths of an inch to about a half an inch, more preferably about a quarter of an inch in diameter. Extensible or resilient cord material or straps of any kind, springs and other elongated materials that can be stretched or preloaded to create a force that can be arranged to exert a downwardly biasing force on the plow blade  330  when the elongated material is interconnected between the mounting apparatus  314  and the plow blade  330  may be used as a resilient elongated member  391  of the present invention. It will be appreciated that multiple resilient elongated members may also be used and the arrangement for interconnecting the plow blade  330  and the mounting apparatus  314  may take any conceivable configuration. 
   Referring now also to  FIGS. 47 and 48 , in certain alternate embodiments, the mounting apparatus  414  of the self-adjusting snow plow  410  will include a mounting frame  409  having a single mounting upright  420 , as shown in these Figures. In  FIG. 47 , the plow blade  430  includes a pair of retention members  438 , similar to those shown in  FIG. 20 , that slideably constrain and/or disengageably secure the plow blade  430  to the single mounting upright  420 . In  FIG. 48 , the plow blade  430 ′ includes a single retention member  438 ′, similar to that shown in  FIG. 22 , that slideably constrains and/or disengageably secures the plow blade  430 ′ to the single mounting upright  420 . 
   Referring now also to  FIG. 40 , because of the light weight of the preferred plow blade, it is relatively easy for an individual to either lift the plow blade  330  from the working orientation, when the plow blade  330  is resting on the ground  56 , or to lower the plow blade  330  to a working position from a non-working orientation similar to that shown in phantom in this Figure. To move the plow blade  330  from the working orientation when the plow blade  330  is engaged with the mounting frame  309  (see, for example,  FIG. 24 ), an individual can start from a position similar to that shown in  FIG. 46  and lift one end of the plow blade using a lifting handle  340 , after disengaging the elongated member  391  from the plow blade  330 , to raise the plow blade  320  high enough to disengage the retention member  338  from the mounting upright  320  on one side of the mounting apparatus  314  and then place the retention member  338  in the attachment member atop the mounting upright  320  on that side of the mounting apparatus  314  so that the plow blade is in a position, similar to that shown in solid line in  FIG. 40 , in between a non-working, transit orientation and a working orientation. To place the plow blade  330  in the non-working, transit orientation, the individual can then go to the other end of the plow blade  330  and lift that end, disengaging the second retention member  338  from the mounting upright  320  on that side of the mounting apparatus  314  and placing the second retention member  338  in the attachment member  351 , so that the plow blade  330  is in the non-working orientation shown in phantom in  FIG. 40 . In preferred embodiments, the steps to lower the plow blade  330  from the non-working, transit orientation to the working orientation are just the reverse. First, the retention member  338  engaged with the attachment member  351  on one side of the mounting apparatus is disengaged and the retention member is engaged for constrained motion along the mounting upright  320  on that side of the mounting apparatus  314  and the end of the plow blade  330  approximate that side of the mounting apparatus  314  is allowed to rest on the ground, so that the plow blade  330  is oriented in the manner shown in solid line in  FIG. 40 . Then the individual can go to the other end of the plow blade and lift it to disengage the second retention member  338  from the attachment member  351  approximate that side of the mounting apparatus  314  and then engage the retention member  338  for constrained motion along the mounting apparatus  320  and lower the second end of the plow blade  330  to the ground. 
   Referring now again to  FIG. 24 , the guide shafts  387  on each side of the plow blade are constructed and arranged to provide the operator of a vehicle pushing the plow blade  330  with markers with which to create a sight line to assist in snow plowing operations. 
   It will be appreciated that the plow blades of the present invention will have many lengths for different purposes. For instance, snow plows for small four wheeled vehicles such as ATV&#39;s and the like may be anywhere from three and a half to six and a half feet, preferably four feet, five feet, or six feet in length. Similarly, the length of the snow plows made for larger vehicle such as trucks, SUV&#39;s and the like may be from six and a half to ten and a half feet, preferably seven feet, eight feet, eight and a half feet, nine feet or even ten feet long. In preferred embodiments, the retention member  38 ,  338 , or slide hinge as it is sometimes called, is preferably made from wire stock (preferably steel) that is from about three eighths to about five eighths inches in diameter, preferably about one half inch in diameter. The retention members  38 ,  338  are attached to respective retention plates that are formed from sheet stock. Preferably, the sheet stock is steel having a thickness of about an eighth of an inch, to which a retention member may be welded. 
   Referring now to  FIG. 24  and  FIG. 25A , the nuts  304 , placed in the attachment channels  301  and  302  are preferably square (having four external flat surfaces), although hex-headed nuts can also be used. In preferred embodiments, the plow blade of the present invention may be easily assembled by factory workers or even consumers who purchase the snow plow in kit form for assembly at home or at the consumer&#39;s workshop. It will be appreciated that the preferred aluminum extrusion shown in  FIG. 24 , does not require any drilling or placement of openings for fasteners. Although not shown, the end caps  346  as well as the cap plates  348  can be predrilled, as well as the cap plates  348 . The guide shafts  387  or sight guides can also come with predrilled holes so that fasteners can be used to secure the guide shafts  387  to the sides of the plow blade proximate the end caps  346  and the end plates  348 . 
   Referring also now to  FIG. 49 , depicting an alternate embodiment of a snow plow blade  530  similar to the hollow core plow blade shown in  FIG. 8 . In this embodiment, the mold board  532  has a first piece  532   a  and a second piece  532   b . As with the previously discussed mold boards, the first or upper mold board piece includes a main or front surface  532   a , a top surface  533   a , a rear surface  538   a  and a bottom surface  547 , which form a hollow or space that can be compartmentalized by a support structure  553 . In addition, the lower or second mold board piece includes constricted channels  549  that are configured to receive fastening elements such as screws. Similarly, the second or lower mold board piece  532   b  includes a main or front surface  532   b , a top surface  548 , a rear surface  538   b  and a bottom surface  533   b , which form a hollow or space that can be compartmentalized by a support structure  555 . In addition, the upper or first mold board piece includes constricted channels  549  that are configured to receive fastening elements such as screws. The two pieces  532   a ,  532   b  include edges that are complimentary shaped to one another to form a tight, interlocking joint and which are further secured together with one or more fasteners  545 , such as a screw or the like that is received in screw hole (not shown) in a groove  546 , shown in  FIG. 50 , in the first mold board piece  532   a . It will be appreciated that the screw can be replaced by other types of fasteners and other kinds of screws, as well, most noticeably, a self-tapping screw that can be screwed directly into the groove  546 , without first creating a pilot hole to accept the screw.  FIG. 50  is a partial, exploded view of the preferred joint configuration created by the edges of the two mold board two pieces  532   a ,  532   b , as also shown in  FIG. 49 . The second piece of  532   b  is preferably secured to the first piece  532   a  by engaging an engaging lip  550  on an upper portion of the second piece  532   b  with a lip-receiving slot  552  on a lower portion of the first piece  532   a . The lip and the slot are provided with angled engagement surfaces, which facilitate alignment and initial engagement of the pieces  532   a ,  532   b . The angled surfaces of the lip and slot also serve to form the tight, interlocking joint by drawing the pieces  532   a ,  532   b  together in a camming action as the plow blade is assembled. As the engaging lip  550  engages the lip-receiving slot  552 , a slot-defining lip  554 , located immediately below and partially defining the slot  552 , engages a second slot  556  located below the engaging lip  550  on the second piece  532   b . At the same time a flange  557  that extends from the rear surface  538   a  to a point below the bottom  547  of the first or upper piece  532   a  engages a recess  558  in rear surface  538   b  adjacent the top  548  of the second or lower piece  532   b . In preferred embodiments, more than one screw, similar to the screw  545  shown in  FIG. 49 , can be used to secure the first piece  532   a  to the second piece  532   b , although these screws are not required because the mold board pieces  532   a ,  532   b  can be held together by retention apparatus assemblies  537 , one of which is shown in phantom in  FIG. 49 . The retention apparatus assemblies  337  are secured side-by-side, in a manner similar to that shown in  FIGS. 8 and 24 , in respective attachment channels  501 ,  502  similar to those shown in  FIG. 25A , but in the first and second pieces  532   a ,  532   b , by threaded bolts  503  (shown in phantom) secured to reciprocally threaded nuts  504  (shown in phantom) in the respective attachment channels  501 ,  502 . 
   Referring now also to  FIG. 51 , a partial, exploded view is shown of a preferred configuration of a rubber scraper  536  and a scraper holding channel  534  further illustrating their complementary shapes and how they are interconnected to better secure the scraper  536  within the channel  534 . There are many other complimentary shapes that are possible, such as the configuration shown in  FIG. 8 , where there are no ridges, or ones where there are a series of ridges on each side. Offset ridges are also possible, but these will require the rubber scraper to be “sided”, or to have “sidedness”, which is less desirable from a point of view of ease of assembly. Other shapes may also be employed, so long as the channel provides some point of restriction that restrains the rubber scraper from downward movement out of the channel. Preferably, the scraper holding channel and rubber scraper will be shaped such that the rubber scraper  536  is sufficiently gripped within the scraper holding channel  534 , even if a fastener is not used. One end of the rubber scraper  536  is positioned within the channel  534  by sliding it into channel  534 , from the side position shown in  FIG. 51 , so that the two ridges  535   a  on either side of the channel  534 , which partially define the channel  534 , accept the rubber scraper  536 . As the channel  534  accepts the rubber scraper  536 , grooves  542  on either side of the preferred rubber scraper  536  slide over respective ridges  535   a . While the rubber scraper  536  can be, and preferably will be, sized to require a friction fit within the channel  534 , it is preferred that the force required to position the scraper  536  within the channel  534  will be that which can be provided with a somewhat forceful push or a series of pushes or shoves given by an assembly worker, or a light tapping with a hard rubber mallet (not shown). Once the preferred rubber scraper  536  is in place within the channel  534 , as shown in phantom in  FIG. 49 , the complimentary grooves  542  and ridges  535   a  act to secure the rubber scraper  536  in place against downward movement. As the rubber scraper either shrinks over time due to aging of the rubber material or shrinks due to cold temperatures, the ridges  535   a  aid in preventing the rubber scraper  536  from being dislodged out of the scraper holding channel  534  in a downward direction. To further secure the rubber scraper  536  within the scraper holding channel  534 , a fastener or a plurality of fasteners of known types and technologies, may be used. In the embodiment shown in  FIG. 49 , the rubber scraper  536  is further secured with a self-tapping screw  540  (shown in phantom) that is inserted through an inflection point  535   b  that runs horizontally across the outside of the mold board  532  on each side, opposite each of the respective ridges  535   a . The self-tapping screw  540  is screwed into and through the mold board  532  and through the scraper holding channel  534  at the grooves  542 . In other embodiments (not shown), the screw can extend through the other side of the mold board  532  at the opposing ridge  535   b , and secured with a nut (not shown). 
   Referring also to  FIG. 52 , this figure illustrates a further preferred embodiment of a plow blade  630  for a further ATV snow plow apparatus (not shown), the plow blade ( 630 ) having one piece mold board  632  having only a main surface  666  and no rear support surface other than a modified retention apparatus  637  (shown in phantom), which includes two metal plates  639  or straps (one of which is shown in phantom), one on each side of the mold board  632 , to which retention members  638  (shown in phantom) are secured, preferably, welded together. The alternate preferred plow blade  630  is intended for use with smaller land vehicles, such as an all terrain vehicle (ATV), a “four-wheeler” or the like. In this embodiment, the single-piece mold board  632  has a main surface  666 , a top  667 , and a bottom  668 . The bottom  668  defines a scraper holding channel  634 , similar to that shown in  FIG. 49 , in which a scraper  636  (shown in phantom) may be inserted and secured in a manner similar to that for the embodiment described above in relation to  FIGS. 49-51 . It will be appreciated, however, that this type of scraper is not a requirement and that other scrapers described herein may also be used. The modified retention apparatus assembly  637  (shown in phantom) is secured to the top  667  of the mold board  632  by a threaded bolt  603  (shown in phantom) that is secured to a nut  604  (shown in phantom) within an upper attachment channel  601  in the mold board  632  in a manner similar to that described in relation to FIGS.  25 A and  49 - 51 , except that there is no lower attachment channel to which to further secure that retention apparatus assembly  637 . Instead, the metal plates  639  will be positioned up against support structures  610  and  611  that extend rearwardly from the main surface  666  or the front  666  of the mold board  632  and preferably secured at the bottom of the mold board  632  by a pair of self-tapping screws  540 , one of which is shown in phantom. In preferred embodiments, the support structures  610 ,  611  will have feet  612  that turn generally about 90° from the support structures  610 ,  611  as shown in  FIG. 52 , so that a force receiving surface  614  is provided on the distal end of each of the feet  612  of the support structures  610 ,  611  to receive and distribute force generated against the metal plates  639  when the vehicle (not shown) presses the mounting apparatus (not shown) against the plow blade  630  to clear snow (not shown) in essentially the same manner as described above in relation to other embodiments of the snow plow apparatus. The force receiving surface  614  of each support structure  610 ,  611  will extend in a generally perpendicular orientation thereto and the support structures  610 ,  611  will extend to the main surface or front  666  of the mold board  632 . In the preferred embodiment illustrated in  FIG. 52 , the mold board  632  includes a plurality support structures  610 ,  611  each including a foot  612  that provides a force receiving surface  614 . In preferred embodiments, each support structure  610 ,  611  will be generally parallel to one another extending away from the front  666  and at least one of the support structures  610 ,  611  is preferably generally perpendicular to the front  666 . In the preferred embodiment shown in  FIG. 52 , the metal plates  639  abut against the force receiving surfaces  614  of the feet  612  of the support structures  610 ,  611  to provide a generally flat pushing surface for the mounting uprights of the mounting frame. In alternate embodiments for light duty vehicles, it will be appreciated that all or almost all of the metal parts of the preferred embodiments could be made of synthetic or natural polymeric materials or other materials other than aluminum and/or steel. Many of these materials are extrudable as is aluminum and its alloys. A preferred rubber scraper  636  (shown in phantom) is secured in a preferred scraper holder channel  634 , similar to that shown in  FIGS. 49 and 51 . The rubber scraper  636  is secured to the mold board  632  with two self-tapping screws  640 , one of which is shown in phantom. The screws are spaced apart along an inflection point on the back of the mold board similar to that discussed in relation to  FIGS. 49 and 50 . 
   Referring now also to  FIGS. 53-54 , a further embodiment of a mounting upright  720  is illustrated for a further embodiment of a mounting frame (not shown) having two mounting uprights. The mounting upright  720  is one of two uprights of the type shown in  FIGS. 7 and 24 , but having an integrally formed slot  722  in which a retention member (not shown) may be inserted. The mounting upright  720  further includes two apertures  778  for receiving a pin  683  (shown in phantom in  FIG. 53 ). When inserted, the pin  683  (shown in phantom) can secure one of the retention members (not shown) in the slot  722 , in a manner similar to that described in relation to pin  383  shown in  FIGS. 26-32 , so that the plow blade (not shown) cannot rise above the pin  683  and become disengaged from the mounting upright  720  when secured within the respective slots  722  of two mounting uprights and in a non-working transit orientation similar to that described in relation to  FIG. 3 . 
     FIGS. 55 ,  56 A and  56 B, illustrate a preferred rubber scraper  736  that will be used primarily with a preferred embodiment of the mold board  632  shown in  FIG. 52 . The preferred rubber scraper  736  is similar to that shown in phantom in  FIGS. 49 and 52  and shown partially in  FIG. 51  in that it includes a bottom edge  737 , a front surface  738 , a rear surface,  739 , a top edge  740 , and side edges, except that the rubber scraper is equipped with a plurality of removably attachable skids  780  (preferably two), one of which is shown in each of  FIGS. 55 ,  56 A and  56 B. Each skid includes a body portion  781  and a flange  782  having one or more apertures  783 . Preferably, the body portion  781  is configured to project rearwardly from the rear surface of the scraper  736  and arranged so that when the scraper is being pushed forwardly against a surface  56  (as in  FIG. 56   a ) the skid  780  does not interfere with the operation of the scraper, and when the plow and the scraper are being dragged in a direction rearward of the plow blade, the exterior surface of the skid  780  lifts the bottom  737  of the scraper  736  above the ground surface  56  (see  FIG. 56   b ). Each skid  780  is preferably removably attached to the rear surface  739 , of the rubber scraper  736  by a pair of threaded bolts  784  which pass through openings  785  in the rubber scraper  736  to secure the skid  780  when the bolts pass through a flat washer  786 , and a lock washer  787  before being secured in a reciprocally threaded nut  788 . 
   Preferably, the body  781  of the skid  780  has an arcuately shaped, rearwardly facing surface. It will be appreciated that the rear surfaces of the skids  780  will protect the bottom edge  737  of the rubber scraper  736  when the rubber scraper  736  is dragged backward along the ground surface  56  as shown in  FIG. 56B , while the skids  780  will have only incidental, limited contact with the ground surface, as shown in  FIG. 56A , when the rubber scraper  736  is pushed forward as will occur when the preferred rubber scraper  736  is employed with a snow plow apparatus including the further preferred mold board  632  and the preferred rubber scraper  736 . 
   It will be appreciated that the materials used and described in the present application are only preferences and that the present self-adjusting snow plow apparatus (including the ATV snow plow apparatus) may be made of many different materials and of materials having a wide variety of thicknesses and sized dimensions. 
     FIG. 57  is a partial, rear perspective view of the plow blade  630  of  FIG. 52  as it may be used in conjunction with the scraper blade  736  of  FIGS. 55-57 . As shown, the plow blade  630  includes support structures  610 ,  611 , which extend rearwardly and which terminate in feet  612  having force receiving surfaces  614 . Note that the support structures are generally, although not necessarily so, parallel, oriented along the longitudinal axis of the plow blade and extend along the width of the plow. The width of the plow blade  630  will be sized appropriately for the intended vehicle to which it will be used. For example, when the snow plow is paired with an all-terrain-vehicle (ATV) it will have a width of about sixty inches, and when the snow plow is paired with a larger vehicle such as a minivan the plow will have a width of about seventy-two inches. As with the previously described embodiments, the plow blade is provided with a retention apparatus  637  that includes a plate  639  having one end that is removably attached to the upper attachment channel  601 , preferably a conventional two part fastener  603 ,  604  (cf. two part fastener  303  and  304  of  FIG. 25A ). The other end of plate  639  may be fastened to the lower end of the plow blade  630  with a self-tapping screw. The plow blade  630  may be used in conjunction with a scraper such as the scraper  736  disclosed in  FIGS. 55 ,  56 A and  56 B, in which the rear surface  739  is provided with one or more removably attachable skids  780 . However, it is understood that any of the other previously discussed scrapers could be used with the plow blade. 
   Generally, when the snow plow blade is constrainingly connected by one or more retention members to the mounting uprights of a mounting apparatus, it will be free to move vertically between the catch structures or retention pins at the upper lower ends of the mounting uprights, and the interconnection member.  FIGS. 58 ,  59 ,  60 , and  61  illustrate an embodiment of the invention in which the snow plow is provided with a multi-function elongated member  800  having a body  802  with a first end  804  and a second end  806 , which is used to adjust a plow blade in one of several positions or modes of operation while the plow blade is constrainingly connected to mounting uprights of a mounting apparatus. The elongated member is designed to be used while the plow blade is attached to a mounting apparatus, which is attached to a subframe  311  (shown in phantom) by fastening elements (not shown) that are inserted through apertures  726  in the interconnecting member  724  and the subframe  311 . Although the elongated member  800  is depicted as being in the form of a flexible strap or webbing, it will be appreciated that other flexible materials such as wires, cords and chains can be used. 
     FIGS. 58 and 59  illustrate a first mode of operation. In the first mode of operation or position, one end  804  of the elongated member  800  is attached to one end of one of the mounting uprights  720  of a mounting apparatus. Preferably, this is achieved by providing the end  804  of the elongated member  800  with a closed loop through which a pin  683  (see, FIGS.  53  and  26 - 28 ) may be inserted when the pin is attached to the upper end of the mounting upright  720 . The body  802  of the elongated member  800  is then fed downwardly through the space between the mounting upright  720  and the retention member  638  that is constrainingly attached thereto. Next, the body  802  is extended along the rear of the plow blade in a direction that is generally parallel to the interconnecting member  724  until it reaches the second mounting upright  720 . The second end  806  is then fed upwardly through the space between the second mounting upright  720  and the retention member  638  that is constrainingly attached thereto and connected to a second pin  683  located at the top of the second mounting upright  720 . Preferably, the second pin  683  has already been attached to the upper end of the second mounting upright  720  and the user need only loop the second end about the second pin  683  and secure the loose end to the body  802  with a fastener  808 , such as a buckle. Once the elongated member  800  has been attached, the user may adjust the length of the member  800 . As the elongated member  800  is shortened, the plow blade will be lifted up from contact with the ground by a distance d 5  (shown in  FIG. 59 ). Stated differently, when the elongated member is shortened the plow blade is prevented from contacting the surface being plowed. That is, the elongated member  800  acts to restrict the downward travel of the plow that would otherwise be available without the elongated member  800 . When the snow plow is positioned in this first operational mode, the plow blade will still be able to function as a snow plow and move snow, but it will now leave a relatively thin layer of snow on the surface it is clearing. As will be appreciated, this is particularly useful in situations where a surface to be cleared is normally covered with gravel or other loose material, because it permits the loose material to remain on the surface while the snow above it is removed. Preferably, this distance d 5  is between ½ to about 4 inches. 
   In a second mode of operation or position, as shown in  FIGS. 60 and 61 , one end  804  of the elongated member  800  is attached to one end of one of the mounting uprights  720  of a mounting apparatus in the manner previously discussed. However, instead of feeding the body  802  downwardly through the space between the mounting upright  720  and the retention member  638 , the body is looped behind the interconnecting member  724 , and then upwardly through the space between the mounting upright  720  and the retention member  638  that is constrainingly attached thereto. Next, the body  802  is extended along the rear of the plow blade in a direction that is generally parallel to the interconnecting member  724  until it reaches the second retention member  638 . Instead of feeding the body  802  upwardly, the body is fed downwardly and looped in front of the interconnecting member  724  and upwardly to the top of the second mounting upright  720 , where it is connected to a second pin  683 . Preferably, the second pin  683  has already been attached to the upper end of the second mounting upright  720  and the user need only loop the second end about the second pin  683  and secure the loose end to the body  802  with a fastener  808 , such as a buckle. Once the elongated member  800  has been attached, the user may adjust the length of the member  800 . As the elongated member  800  is shortened, the plow blade will be prevented from contacting the catch structures or retention pins. That is, the elongated member  800  acts to restrict the upward travel of the plow that would otherwise be available without the elongated member  800 . As will be appreciated, this will not substantially affect the operation of the snow plow when the snow plow is being dragged in a direction rearward of the plow blade because the plow blade may still pivot about the retention member—mounting upright connections. However, when the snow plow is pushed forwardly and it contacts snow or the surface being cleared, the resistance exerted against the plow blade will tend to pivot it about the retention member connections until the bottom of the plow blade substantially abuts the mounting uprights. As the plow blade pivots into position, its upper range of motion would normally be limited by the catch structures or retention pins. However, when the elongated member is in its second position, the upper range of motion is foreshortened and the snow plow will tend to lift the entire mounting assembly, rather than float relative to the mounting uprights. When this occurs, the weight of the vehicle can be transferred from the wheels to the plow. As will be appreciated, a considerable downward force may be applied to the plow blade; on the order of up to 3-400 pounds. This extra force is particularly useful when the snow plow is used on improved roads or surfaces such as sidewalks. 
   The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described herein, the details may be changed without departing from the intended scope of the invention, which is defined by the attached claims.