Patent Abstract:
A spring assembly defining an elongated axis and includes an axially elongated connector articulately connected toward a first end to a first member and articulately connected toward a second end to a second member for joining and permitting pivotal movements between the first and second members. Two springs are arranged axially relative to each other along and about the connector between the first and second ends thereof. An alignment member is disposed between the two springs for aligning adjacent ends of the two springs relative to each other and relative to an elongated axis of the spring assembly. The alignment member defines a generally centralized opening adapted to slidably move along and relative to the connector.

Full Description:
FIELD OF THE INVENTION DISCLOSURE 
       [0001]    The present invention disclosure generally relates to a spring assembly for a plow mechanism and, more particularly, to a plow mechanism spring assembly having two axially arranged springs with an alignment guide disposed therebetween for aligning adjacent ends of the springs relative to each other and relative to an elongated axis of the spring assembly 
       BACKGROUND 
       [0002]    Spring assemblies are used in myriad of different environments. In one form, spring assemblies are used in connection with plows on railcars. In another form, spring assemblies are known to be used in combination with snow plows on light and medium trucks. The business of manufacturing plows for trucks is highly competitive, with manufacturers differentiating themselves based on features and enhanced technology they design into their products. 
         [0003]    When plowing a street or parking lot, it is not infrequent for a lower edge of the plow to strike an object which is concealed beneath the snow. This occurs particularly often when a displaced manhole/sewer cover is forcibly struck or engaged during a plowing operation. Alternatively, the plow blade can strike various objects while plowing a road which is not paved, for example, gravel or dirt roads. Since the roads being plowed are typically frozen, it is common for an object of significant size to become frozen into the road. As an example, medium size rocks which would normally not pose a problem when laying loose on the road, can and often do present a problem, when they are frozen into the surface of the road and concealed beneath a layer of snow. Additionally, when the snow fall accumulates, it tends to hide or otherwise conceal obstacles such a curbs, dividers and the like, which an operator may not see or can misconstrue the significance thereof resulting in the snow plow being mistakenly driven thereinto sometimes with considerable force. 
         [0004]    Accordingly, snow plow blades have been manufactured with a blade trip mechanism. Such a mechanism allows the plow blade to pivot or otherwise rotate so as to allow the plow blade to yield upon substantial impact with an object. That is, and upon striking an object and/or obstruction, such a mechanism permits a bottom of the snow plow blade to pivot rearwardly from a normal plowing position. Simultaneously, and as the bottom of the snow plow blade pivots rearwardly, the top of the snow plow blade moves forward from the normal plowing position. 
         [0005]    Movement between the normal plowing position of the snow plow blade to a position in which the bottom of the snow plow blade pivots rearwardly or backward is commonly referred to as blade tripping. Movements of the snow plow blade from a normal plowing position to a “blade tripped” position is resisted by two or more trip springs mounted behind the snow plow blade. Each spring extends from a position wherein the spring is connected toward a top of the snow plow blade to frame structure used to connect the plow blade to a vehicle. When the bottom of the snow plow blade is forced backward, the springs provide a strong resistance to the movement while tending to absorb some of the impact forces of the of the snow plow blade with the object which has been engaged and struck. 
         [0006]    When the force causing the snow plow blade to trip are removed, i.e, after the object being struck has been overcome, the springs forcibly urge the snow blade to return to the normal plowing position, also referred to as the “blade return” position. Since it is not desirable for the snow plow blade to be easily moved from the normal plowing position when plowing snow, the springs are quite strong. Moreover, and depending upon the size or height of the snow blade and the location on the frame wherein the springs are connected thereto, the springs often have an extended length. Although necessary for proper operation of the plow assembly, their extended length coupled with the strength required thereof makes such springs expensive. 
         [0007]    Thus, there is a continuing need and desire for an elongated spring assembly which provides both the necessary strength and durability and yet is economical to produce and replace whereby reducing maintenance costs associated with such plows. 
       SUMMARY 
       [0008]    In view of the above, and in accordance with one aspect of this invention disclosure, there is provided an axially elongated spring assembly for releasably maintaining a plow blade in a predetermined position about a generally horizontal axis. The spring assembly includes an elongated retractable/extendable connector arranged in general coaxial alignment with an elongated axis of the spring assembly. A first end of the connector is operably connected to the plow blade at a location disposed above the generally horizontal axis; with a second end being operably connected to a plow blade frame. Two springs, arranged in axial relation relative to each other, are disposed between the first and second ends of and along the connector. An alignment member is disposed between adjacent ends of the two springs. The alignment member defines a generally centralized opening so as to permit the guide to slidably move along and relative to the connector while maintaining alignment of adjacent ends of the two springs relative to each other and relative to the elongated axis defined by the spring assembly. 
         [0009]    Preferably, each spring of the spring assembly is formed from an axially elongated one-piece elastomeric material defining an elongated bore opening to opposed ends thereof. The elongated bore defined by each spring preferably has a closed margin about a diameter thereof. In one form, the each spring has a plurality of axially spaced flange sections along a length thereof, with any two axially adjacent flange sections on each spring being axially separated by an axially elongated energy absorption section for allowing each spring to react to energy imparted thereto during operation of said spring assembly. 
         [0010]    In one embodiment, the alignment member defines an opening extending therethrough, with a marginal edge of the opening having a cross-sectional configuration which proximates a cross-sectional configuration of the elongated connector. Each spring of the spring assembly has interior and exterior surfaces In this form, the alignment member has a body portion with projections axially extending away from opposed and generally parallel surfaces on the body portion and arranged in generally concentric relation with the elongated axis defined by said spring assembly. Each projection on the alignment member preferably defines an exterior surface sized to axially extend within and operably engage the interior surface of a respective spring to affect alignment between the adjacent ends of the two springs relative to each other and relative to the elongated axis defined by the spring assembly 
         [0011]    According to another aspect of this invention disclosure, there is provided biasing structure arranged in combination with a plow blade assembly having a frame defining a longitudinal axis. The frame mounts a plow blade for pivotal movement about a generally horizontal axis between a blade return position and a blade tripped position. The biasing structure urges the plow blade from the blade tripped position toward the blade return position and includes a pair of laterally spaced spring assemblies disposed to opposed lateral sides of the longitudinal axis defined by the plow blade frame. Each spring assembly includes an extendable/retractable connector defining an elongated axis. A first end of the connector is operably joined to the plow blade above the axis about which the plow blade pivots and a second end of the connector is operably joined to the frame. First and second end-to-end springs are arranged in operable combination with and along a lengthwise portion of each connector for biasing the plow blade from the blade tripped position toward the blade return position. An alignment member is disposed between the first and second springs of each spring assembly for aligning adjacent ends of the springs relative to each other and relative to the elongated axis of the connector. The alignment member defines a generally centralized opening adapted to slidably move along and relative to the connector. 
         [0012]    In one form, the springs of each spring assembly are formed from an axially elongated one-piece elastomer defining an elongated bore opening to opposed ends thereof. The elongated bore defined by each compression spring preferably has a closed margin. In the illustrated embodiment, each spring has a plurality of axially spaced flange sections along a length thereof, with any two axially adjacent flange sections on each spring being axially separated by an axially elongated energy absorption section for allowing each spring to react to energy imparted thereto during operation of the spring assembly. 
         [0013]    The opening in the alignment member of each spring assembly preferably has a marginal edge with a cross-sectional configuration which proximates a cross-sectional configuration of the respective elongated connector. Also, the spring of each spring assembly has interior and exterior surfaces. Moreover, in one form, the alignment member of each spring assembly has a body portion with projections axially extending away from opposed and generally parallel surfaces on the body portion and arranged in generally concentric relation with the elongated axis defined by the respective spring assembly. In one form, the projections on the alignment member of each spring assembly each define an exterior surface sized to axially extend within the interior surface of a respective spring to effect alignment between the opposed ends of the two springs of the respective spring assembly relative to each other and relative to the elongated axis defined by the spring assembly 
         [0014]    According to yet another aspect, there is provided an axially elongated spring assembly defining an elongated axis and includes an elongated multipiece connector whose first end is articulately joined to a first member and articulately joined toward a second end to a second member to permit pivotal movements between the first and second members. Two springs are arranged axially relative to each other along and about the connector between the first and second ends thereof. An alignment member is disposed between the two springs to effect alignment of adjacent ends of the two springs relative to each other and relative to an elongated axis of the spring assembly. The alignment member defines a generally centralized opening adapted to slidably move along and relative to the elongated connector. 
         [0015]    In one form, each spring is formed from an axially elongated one-piece hollow elastomer opening to opposed ends. The elongated bore defined by each spring preferably has a closed margin about a diameter thereof. In a preferred form, each spring has a plurality of axially spaced flange sections along a length thereof, with any two axially adjacent flange sections on each spring being axially separated by an axially elongated energy absorption section for allowing each spring to react to energy imparted thereto during operation of said spring assembly. 
         [0016]    Preferably, a marginal edge of the opening in the alignment member of each spring assembly has a cross-sectional configuration which proximates a cross-sectional configuration of the elongated connector. Moreover, each spring has interior and exterior surfaces In one embodiment, the alignment member has a body portion with projections axially extending away from opposed and generally parallel surfaces on the body portion and arranged in generally concentric relation with the elongated axis defined by the spring assembly. The projections on the alignment member preferably defines an exterior surface sized to axially project within the interior surface of a respective spring to affect alignment between the opposed ends of the two springs relative to each other and relative to the elongated axis defined by the spring assembly 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a side elevatonal view of a spring assembly in accordance embodying principals and teachings of this invention disclosure forming part of a plow assembly mounted to a light duty vehicle such as a pick-up truck; 
           [0018]      FIG. 2  is a fragmentary top plan view of the plow assembly shown in  FIG. 1 ; 
           [0019]      FIG. 3  is a schematic and enlarged side elevational view showing a plow blade in a lower operating position; 
           [0020]      FIG. 4  is a schematic view similar to  FIG. 3  showing the plow blade in a raised and deflected position; 
           [0021]      FIG. 5  is a plan view of an alignment guide forming part of the present invention disclosure; and 
           [0022]      FIG. 6  is a cross-sectional view taken along line  6 - 6  of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    While this invention disclosure is susceptible of embodiment in multiple forms, there is shown in the drawings and will hereinafter be described a preferred embodiment, with the understanding the present disclosure sets forth an exemplification of the disclosure which is not intended to limit the disclosure to the specific embodiment illustrated and described. 
         [0024]    Referring now to the drawings, wherein like reference numerals indicate like parts throughout the several views, there is shown in  FIGS. 1 and 2  a plow assembly, generally indicated by reference numeral  10 , which includes a universal mounting or frame assembly  20  having a plow blade  40  connected toward a forward end thereof. Although the present invention disclosure is shown for illustrative purposes as part of a plow assembly which, in turn, is mounted or otherwise connected to a front end of a vehicle, generally identified by reference numeral  12  ( FIG. 1 ), it should be appreciated the principals and teachings of the present invention disclosure can find utility in applications and uses other than that shown. 
         [0025]    Frame assembly  20  is of a conventional design. In the embodiment illustrated for exemplary purposes, and as shown in  FIG. 2 , the frame assembly  20  for operably connecting the plow blade  40  to the vehicle  12  ( FIG. 1 ) defines a longitudinal axis  22  and includes a pair of arms  23 ,  24  arranged in a generally V-shape relative to each other and which permit the plow blade  30  to be raised and lowered, when required or desired. To affect such ends, and as shown in  FIG. 1 , frame assembly  20  includes a conventional lift mechanism  26  including a distendable/retractable driver  27  attached to a pivotal lever  28 . In one form, one end of a chain  30  is operably connected toward a free or distal end of the lever  28 . The other end of the chain  30  is connected to the frame arms  23 ,  24 . Selective operation of the driver  27  causes the arms  23 ,  24  to pivot whereby raising and lowering the plow blade  40  to a desired position. 
         [0026]    The plow blade  40  has a front clearing surface  42 , concave in the direction of movement, a lower scrapper edge  44 , an upper edge  46 , and a rear side or surface  48 . The blade  40  is attached toward a front of the frame assembly  20  in a conventional and well known manner so as to permit the plow blade  40  to pivot about a generally horizontal axis  50  located to the rear side  48  of the plow blade  40 . Suffice it to say, the plow blade  40  is mounted to the frame assembly  20  such that it may pivot between a blade trip return position, shown in  FIG. 3 , and a blade tripped position, shown in  FIG. 4 . 
         [0027]    It will be appreciated by those skilled in the art, and during operation of the plow assembly  10 , when the edge  44  of the plow blade  40  strikes or hits an object on the ground sufficiently hard, it will be driven from the blade return position shown in  FIG. 3  to the blade tripped position shown in  FIG. 4 . That is, in the event the blade  40  strikes an obstruction sufficiently hard, the lower edge  44  moves upward and pivots rearward about axis  50  while the upper edge  46  will pivot or rotate forward about axis  50  as the plow  40  is driven from the blade return position shown in  FIG. 3  to the blade tripped position shown in  FIG. 4 . This forward tilt allows blade  40  to slide up and over the obstruction. 
         [0028]    To bias plow blade  40  toward the blade return position ( FIG. 3 ) and to resist movement of the plow blade into the blade tripped position ( FIG. 4 ), biasing structure  60  is arranged in operable combination with blade  40 . In the embodiment shown in  FIG. 2 , biasing structure  60  includes first and second spring assemblies  62  and  62 ′ preferably arranged generally parallel to each other and to opposed lateral sides of the longitudinal axis  22  of frame assembly  20 . It will be appreciated, more than two spring assemblies can be utilized to form the biasing structure  60  if so desired without detracting or departing from the spirit and scope of this invention disclosure. Preferably, the spring assemblies  62 ,  62 ′ are substantially similar relative to each other and, thus, only spring assembly  62  will be described in detail. 
         [0029]    In the embodiment shown in  FIG. 3 , each spring assembly defines an elongated axis  64  and includes an elongated retractable/extendable connector  66  preferably arranged in general coaxial alignment with the elongated axis  64  of the spring assembly. Suffice it to say, connector  66  is designed and constructed to permit movement of the blade  40  between the blade return position ( FIG. 3 ) and the blade tripped position ( FIG. 4 ). Preferably, and as shown in  FIG. 2 , the axis  64  of each spring assembly  62 ,  62 ′ is disposed generally parallel to the longitudinal axis  22  of frame assembly  20 . As such, the spring assemblies  62 ,  62 ′ preferably do not pull in a direction which is at an angle relative to the longitudinal axis  22  of the frame assembly  20 . Such a design offers a major advantage over previously known spring arrangements which are disposed at an angle relative to the longitudinal axis  22  of the frame assembly. By arranging the spring assemblies generally parallel to the longitudinal axis  22  of frame assembly  20  substantially all the spring force of the spring assemblies is utilized for the blade trip operation. Such a design provides more consistent blade trip operation. Moreover, such design eliminates almost all lateral trip spring force from being exerted on the frame assembly  20  of the plow assembly. 
         [0030]    In the illustrated embodiment, connector  66  is of multipiece construction and includes a first axially elongated member or piece  68  which is operably joined or otherwise attached to a second axially elongated piece  70 . The connector pieces  68 ,  70  are operably interconnected to each other so as to permit extension/retraction of each spring assembly during operation of the plow assembly  10 . 
         [0031]    As illustrated in  FIGS. 3 and 4 , a first end  76  of connector  66  is operably and articulately joined or attached to the plow blade  40  at a location disposed above the horizontal axis  50  about which the blade  40  pivots. A second end  78  of connector  66  is operably and articulately connected to the frame assembly rearward of the rear side  48  of plow blade  40 . 
         [0032]    As shown in  FIG. 3 , and spaced axially away from that end  76  articulately connected to blade  40 , connector piece  68  is provided with a first fixed radial flange or stop  80 . Similarly, and spaced axially away from that end  78  articulately connected to frame assembly  20 , connector piece  70  is provided with a second fixed radial flange or stop  84  disposed in axially spaced relation from stop  80 . The axial distance between flanges  80  and  84  on connector  66  can vary depending upon any of a number of factors. That is, the axial distance between flanges  80  and  84  on connector  66  can vary depending upon the particular plow design. Moreover, the axial distance between the connector flanges  80  and  84  can vary depending upon the obstruction being struck and the disposition of the plow blade when it reaches the blade tripped position. Suffice it to say, the axial distance separating the flanges  80  and  84  on connector  66  can range between about 24 inches and about 40 inches during operation of the plow blade assembly  10 . 
         [0033]    In one form, the radial flange or stop  80  is arranged generally coaxial with the longitudinal axis  64  of the respective spring assembly and defines a projection  81  extending axially inward toward a longitudinal center of the respective spring assembly. In the illustrated embodiment, the projection  81  defines a radial shoulder  82  having an outside diameter which is smaller than an outer diameter of stop  80  so as to allow the projection  81  to axially extend within an interior of a spring  90  and provides the stop  80  with a step  83 . 
         [0034]    In one form, the radial flange or stop  84  is arranged generally coaxial with the longitudinal axis  64  of the respective spring assembly and defines a projection  85  extending axially inward toward a longitudinal center of the respective spring assembly. In the illustrated embodiment, the projection  85  defines a radial shoulder  86  having an outside diameter which is smaller than an outer diameter of stop  84  so as to allow the projection  85  to axially extend within the interior of the interior of a spring  90 ′ and provides the stop  84  with a step  87 . 
         [0035]    As shown in  FIG. 3 , operably disposed between the opposed ends of connector  66 , each spring assembly  62  includes first and second axially aligned springs  90  and  90 ′. It should be appreciated, however, if and when required, each spring assembly can include more than two springs arranged in end-to-end relationship without detracting or departing from the spirit and scope of this invention disclosure. In the illustrated embodiment, springs  90 ,  90 ′ are designed as compression springs that are axially arranged in operable combination with and between the stops  80  and  84  on connector  66  such that springs  90 ,  90 ′ extend along and about a lengthwise portion of the connector  66  and bias the plow blade  40  from the blade tripped position ( FIG. 4 ) toward the blade return position ( FIG. 3 ). 
         [0036]    As shown, springs  90 ,  90 ′ are substantially similar in design relative to each other and, thus, only spring  90  will be described in detail. Preferably, each spring has an axially elongated body  92  with a generally cylindrical configuration between opposed ends. Moreover, each spring is generally hollow and defines an elongated bore  94  opening to opposed ends of the respective spring whereby providing each spring with interior  95  and exterior surfaces  97 . As shown, the bore  94  defined by each spring has a closed margin about a diameter thereof. Although not specifically shown, it should be appreciated, the principals and teachings of the present invention disclosure equally apply to metal coil springs. 
         [0037]    In the preferred form, each spring  90 ,  90 ′ is formed from an axially elongated one-piece thermoplastic ether ester elastomer. In the illustrated embodiment, each spring  90 ,  90 ′ is provided with a plurality of axially spaced flange sections  96  along a length thereof. Preferably, the flange sections  96  of each spring  90 ,  90 ′ has a generally constant outside diameter. As shown in  FIG. 3 , any two flange sections  96  on each spring  90 ,  90 ′ are axially separated by an energy absorbing section  98  for allowing the spring to react to energy imparted thereto during operation. Each energy absorbing section or convolute  98  of each spring  30  preferably has the form of a ring whose lateral outer face is curved toward an exterior of the respective spring. 
         [0038]    The thermoplastic ether ester elastomer used to form springs  90 ,  90 ′ is initially created as a preform. An elastomer having tensile characteristics such that the ratio of plastic strain to elastic strain is greater than 1.5 to 1 has proven particularly beneficial. The preferred elastomer is one manufactured and sold by E.I. duPont de Nemoirs under the trademark Hytrel®. Notably, however, suitable elastomer materials other than Hytrel® would equally suffice without detracting or departing from the spirit and scope of this disclosure. Notably, the elastomer material forming the elastomer is free of spring-like characteristics. For a more complete description of transmuting such elastomer material into a spring, attention is directed to U.S. Pat. No. 4,198,037 to D. G. Anderson and/or U.S. Pat. No. 5,141,697 to N. E. Wydra; with applicable portions of either and/or both references being incorporated herein by reference. 
         [0039]    Preferably, the elastomer used to form springs  90 ,  90 ′ has a molecular structure and a Shore D durometer hardness ranging between about 40 and 60. In the preferred embodiment, the elastomer used to form springs  90 ,  90 ′ has a Shore D durometer of about 55. Significantly, such elastomer is quite durable and has an excellent flex life. Moreover, such elastomer is not subject to tearing or to crack propagation even in relatively thin cross-sections. Additionally, such an elastomer is known to work well in a wide range of temperature variants 
         [0040]    Preferably, and after being arranged in operable combination with spring  90 , the step  83  on stop  80  operably engages and acts as a seat for an outer end of spring  90 . Moreover, and after being arranged in operable combination with spring  90 , projection  81  on stop  80  will axially extend into the interior of spring  90  such that the outer diameter of the projection  81  generally aligns one end of spring  90  relative to the elongated axis  64  of the respective spring assembly. Similarly, and after being arranged in operable combination with spring  90 ′, the step  87  on stop  84  operably engages and acts as a seat for an outer end of spring  90 ′. Moreover, and after being arranged in operable combination with spring  90 ′, projection  85  on stop  84  axially extends into the interior of spring  90 ′ such that the outer diameter of the projection  84  generally aligns one end of spring  90 ′ relative to the elongated axis  64  of the respective spring assembly. Notably, an outer diameter of each stop  80 ,  87  is larger than the outer diameter of each spring  90 ,  90 , respectively. 
         [0041]    After being arranged about and along the respective connector  66 , and to advantageously align axially adjacent inner ends of the springs  90 ,  90 ′ relative to each other and relative to the elongated axis  64  of each spring assembly whereby optimizing performance of the biasing structure  60 , each spring assembly furthermore includes an alignment member  100 . In the embodiment shown in  FIGS. 5 and 6 , alignment member  100  includes a body portion  102  having an outer diameter generally equal to or somewhat larger than the outer diameter of each spring  90 ,  90 ′. 
         [0042]    Alignment member  100  further includes projections  108  and  118  axially extending away from opposed and generally parallel surfaces  104  and  106  of the body portion  102 . The generally parallel surfaces  104  and  106  on alignment member  100  preferably engage and acts as seats for an inner end of springs  90 ,  90 ′, respectively. Notably, in a preferred form, the body portion  102  defines a centralized axis  107  with the projections  108  and  118  being arranged in generally concentric relation relative to the centralized axis  107 . Projection  108  has a diameter smaller than an outside diameter of member  100 . As such, projection  108  defines a radial shoulder  110  with a diameter equal to or slightly smaller than the interior surface  95  of spring  90 . Similarly, projection  118  has a diameter smaller than an outside diameter of member  100 . As such, projection  118  defines a radial shoulder  120  having a diameter equal to or slightly smaller than the interior surface  95  of spring  90 ′. 
         [0043]    As shown in  FIGS. 5 and 6 , alignment member  100  further define a generally centralized opening  124  extending through the body portion  102 , through the projections  108  and  118 , and opening to opposed sides of member  100 . The opening  124  has a predetermined marginal configuration which preferably proximates the cross-sectional configuration of the connector  66  ( FIGS. 3 and 4 ) extending axially therethrough. As such, and when mounted in operable combination with the respective spring assembly of biasing structure  60  ( FIGS. 3 and 4 ), the alignment member  100  is permitted to slide along the length of the connector  66  while maintaining a predetermined rotational orientation with respect to the connector  66 . In  FIGS. 5 and 6 , the marginal configuration of opening  124  is illustrated as being generally square. It should be appreciated, however, the marginal configuration of opening  124  can be other than square i.e. triangular, rectangular, oval and etc without detracting or departing from the spirit and scope of this invention disclosure. 
         [0044]    As shown in  FIGS. 3 and 4 , when arranged in operable combination with springs  90 ,  90 ′ of each spring assembly, projection  108  on alignment member  100  axially extends into the interior surface  94  of spring  90 ′ so as to allow surface  104  to engage with the abutting end of spring  90  while the radial shoulder  110  on projection  108  effects alignment of spring  90  relative to the elongated axis  64  of the respective spring assembly. Similarly, projection  118  on member  100  will axially extend into the interior surface  94  of spring  90 ′ so as to allow surface  106  to engage with the abutting end of spring  90 ′ while the radial shoulder  120  on projection  118  effects alignment of spring  90 ′ relative to the elongated axis  64  of the respective spring assembly. 
         [0045]    During operation of the plow assembly  10 , and in the event the plow blade  40  strikes an obstruction, forward rotation or roll of the upper portion of the blade  40  about axis  50  temporarily lengthens the connector  66  and blade  40  is moved toward the blade tripped position schematically represented in  FIG. 4 . As such, and as schematically shown in a comparison of  FIGS. 3 and 4 , the axial distance between the first and second stops  80  and  84  is shortened resulting in compression of the springs  90 ,  90 ′ of each spring assembly  62  of the biasing structure  60 . Notably, however, and to optimize spring performance and operation, although the springs  90 ,  90 ′ are compressed, the alignment member  100  slides along the length of the connector whereby maintaining the inner ends of the springs  90 , 90 ′ in generally axial alignment with each other and relative to the elongated axis  64  of the respective spring assembly  62 . After the obstruction is overcome, the forces acting to displace the blade to the tripped position are overcome by the spring assemblies comprising biasing structure  60 . That is, the forces applied by the spring assemblies of the biasing structure  60  tend to forcibly return or restore blade  40  to the blade return position ( FIG. 3 ). 
         [0046]    It may therefore be appreciated from the above detailed description of the preferred embodiment of the present invention disclosure that it teaches a biasing structure having two axially arranged spring assemblies each of which includes a plurality of axially disposed springs and an alignment guide for maintaining adjacent inner ends of the springs  90 ,  90 ′ in generally aligned relation relative to each other and relative to an elongated axis of the spring assembly. In one form, the biasing structure is used to return a plow blade from a blade tripped position to a blade return position with consistency and regularity. The use of two springs arranged in end-to-end relation relative to each other economizes on the cost to manufacture the spring assembly without detracting from its performance. In most applications, Applicants have advantageously discovered it is more economical to use two shorter length springs in end-to-end combination relative to each other rather than having to manufacture a one-piece spring having the same effective length. Moreover, constructing such spring assemblies with two elastomeric end-to-end springs renders a design which is both durable and long lasting while requiring minimal maintenance in a myriad of different ambient weather conditions. Additionally, the ability to change the force required to move or roll the plow blade to a blade tripped position can be adjusted both readily and inexpensively by simply changing one or both of the elastomeric springs comprising the biasing structure. 
         [0047]    From the foregoing, it will be observed that numerous modifications and variations can be made and effected without departing or detracting from the true spirit and novel concept of this invention disclosure. Moreover, it will be appreciated, the present disclosure is intended to set forth an exemplification which is not intended to limit the disclosure to the specific embodiment illustrated. Rather, this disclosure is intended to cover by the appended claims all such modifications and variations as fall within the spirit and scope of the claims.

Technology Classification (CPC): 5