Abstract:
A pavement grinding apparatus moves along a direction of travel and includes a cutting assembly. The cutting assembly has a grinding carriage; the grinding carriage including a rotating arbor having cutting elements. A control wheel is in contact with the pavement and connected to the grinding carriage to impart a cyclical up and down movement to the grinding carriage. The control wheel includes equally spaced apart lobes on the periphery of the control wheel that move the arbor in a sinusoidal up and down pattern.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention is directed to an apparatus for forming a sonic noise alert pattern (SNAP) in the surface of the road, and in particular, to a high speed grinder for forming a series of spaced apart sinusoidal depressions in pavement. 
         [0003]    2. Prior Art 
         [0004]    Rumble strips or sonic noise alert pattern (SNAP) depressions in the surface of the road are well known and widely referred to as rumble strips. Such depressions generate an easily heard noise when a vehicle tire drives over such a stretch of pavement. In addition, vibration is usually passed to the driver and passengers of the vehicle, alerting them that they have passed over such a pattern of depressions. Such SNAP depressions are often placed at the side of the road on the shoulder or along the centerline of two lane roads to alert a driver that the vehicle has veered off the driving lane, as may happen when drivers fall asleep at the wheel. In addition, rumble strips are placed across the width of the lanes of the road to alert the driver that he/she is approaching a stop or reduced speed limit and to slow down in anticipation of the upcoming reduced speed or stop. 
         [0005]    It can be appreciated that forming such depressions in the road typically requires a grinding device that must rise and fall in a predetermined cycle to create a series of substantially evenly spaced apart depressions. For very hard pavement surfaces, such as concrete surfaces, the power required is substantial in order to form the depressions. The speed of forming such depressions is generally quite slow, on the order of a several hundred feet per minute. When miles of such SNAP depressions must be formed in the road, the work can be a very time consuming process. In addition to the time required, the costs become substantial for a crew and the grinding equipment. Besides the costs of forming the strips, the inconvenience to drivers using the road, including lane closures, can be substantial, causing severe traffic delays. 
         [0006]    A known device for forming such strips is shown in U.S. Pat. No. 6,499,809. This patent shows a device and method for making SNAP depressions in the surface of pavement. The pavement grinder has a grinding arbor supported on transverse parallel shafts with an offset to produce an up and down reciprocal motion to raise and lower the grinding carriage and form depressions in the pavement. 
         [0007]    Another device for cutting depressions in the road is shown in U.S. Pat. No. 5,297,894, to Yenick. The Yenick patent shows a pivotally mounted cutting head with a pair of guide wheels and a cam at the rear of the cutting device to raise and lower the cutting head. The cam includes a chain arrangement to raise and lower the cutting head to the proper depth. However, the pivoting arrangement does not provide sufficient power or speed for the cutting head for some applications. The Yenick device requires the cutting head to follow a cam member with a wheel engaging the outer periphery of the cam. 
         [0008]    Although rumble strips have proven effective at alerting drivers when their vehicles is drifting from the driving lane, the noise generated may be too loud and may be a nuisance to those close to the rumble strips. In some cases, rumble strips have been filled in to deal with the excessive noise. However, this eliminates the safety benefits provided by the rumble strips. Much of the noise is due to the wheel entering and leaving each depression as typical depressions do not have a gradual transition to and from the road surface. 
         [0009]    In an effort to provide a satisfactory warning to drivers while producing less noise than conventional rumble strips, warning strips that still produce a vibration at a lower noise volume have been developed. Such quieter patterns, referred to as mumble strips, may be placed in the same locations as conventional rumble strips and produce a vibration and noise, but are quieter when vehicles pass over the patterns. To produce less noise, the mumble strips are formed by recesses with a more gradual entry and exit transition for each recess. The pattern of recesses therefore takes on a continuous sinusoidal pattern. Such a pattern eliminates sharp edges that may be formed at the entry into and exit from each recess, resulting in a quieter pattern, but still providing sufficient warning to drivers. It can be appreciated that grinding such a pattern requires a gradual engagement and disengagement of the grinding head rather than a plunge cut and may be difficult to obtain. 
         [0010]    It can be seen then, that a new and improved method and apparatus for cutting evenly spaced apart sinusoidal depressions in the surface of pavement to form a sonic noise alert pattern is needed. Such a grinding device should provide for directly lowering and raising the cutting head in a continuous repeating pattern with a gradual entry and exit to and from each recess. A grinder should have a simple and reliable construction that provides sufficient power and direct support for raising and lowering the cutting head in a predetermined pattern at sufficient speed to cut even hard pavement material at speeds of over one mile per hour. The present invention addresses these as well as other problems associated with cutting a series of sonic noise alert pattern depressions in the surface of the pavement. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention relates to an apparatus and method for forming rumble strips, also known as Sonic Noise Alert Pattern (SNAP) depressions in the surface of the road. In particular the present invention relates to an apparatus and method for quieter reduced volume rumble strips, sometimes referred to as mumble strips. 
         [0012]    The grinding apparatus includes a truck chassis that supports a grinding carriage on its own movable frame. The grinding carriage has a cutting assembly that can be moved between a raised travel position and a lowered cutting position. The cutting assembly includes an arbor which includes carbide teeth mounted along and around the arbor. The width of depressions ground in the pavement is variable depending on the number and arrangement of the teeth mounted on the arbor. The arbor mounts to the grinding carriage of the cutting assembly. The grinding carriage includes motors and a drive train to drive the arbor and may include belts, chains or may have motors directly mounted to the arbor shaft. The cutting assembly may also include a cooling system typically providing cooling water for the arbor to prevent the cutting teeth from overheating and to control dust. The grinding carriage has a control wheel that is coupled to the arbor to control up and down motion of the arbor. 
         [0013]    The grinding carriage mounts to the rear of a chassis, such as a truck chassis, on a support assembly that provides for adjusting the lateral position of the grinding carriage relative to the chassis. With such adjustment the chassis can be driven in a safe and efficient position on a road that minimizes traffic disruption, keeps the pavement grinder in a safe path of travel, allows the driver to view the grinding carriage operate and keeps the arbor cutting a pattern at the correct location on the pavement. 
         [0014]    The control wheel is a non-round wheel formed by a tire mounted on a rim. The tire is a solid element and made of compound having minimal to low compression even when subjected to the forces associated with pavement grinding. The periphery of the tire is non-round and the diameter varies in an undulating repeated pattern. The pattern is sinusoidal and wraps around the periphery of the tire. In one embodiment, the tire forms three lobes of maximum diameter. The lobes alternate with three depressions of minimum diameter. The areas between the lobes and the depressions gradually transition in the sinusoidal pattern. In the embodiment shown, the diameter varies one quarter inch, between twelve and three-quarter inches at the depressions and thirteen inches at the maximum height of the lobes. The distance between adjacent depressions, which is also the distance between the peaks of the lobes, is fourteen and one-half inches. As the depressions and the lobes are evenly spaced about the periphery of the tire, the distance between any two lobes and the distance between any two depressions is the same fourteen and one-half inches. 
         [0015]    In use the control wheel controls the up and down movement of the cutting assembly and the depth with which the arbor grinds. The control wheel has a non-circular outer periphery with increasing and decreasing diameter around the wheel in an evenly spaced pattern. The control wheel has lobes of increased diameter alternates with three depressions of decreased diameter. The outer periphery gradually transitions from the depressions to the lobes. The gradual increase and decrease follows a sinusoidal pattern extending around the periphery of the control wheel. The varying diameter causes the center axis, and therefore the axle, of the control wheel to rise and fall. The control wheel axle rises relative to the ground when one of lobes is in contact with the ground surface while the axle lowers when one of the depressions engages the ground. The height of the axis of rotation rises and falls as the control wheel contact point transitions between the maximum at the apex of the lobes and the trough at the bottom of the depressions. 
         [0016]    The cutting assembly is coupled to the control wheel so that the elevation of the arbor rises and falls with the height of the axle of the control wheel. The arbor also rises and falls in a sinusoidal pattern matching the pattern on the control wheel. The rising and falling causes the arbor to grind a sinusoidal pattern in the pavement. 
         [0017]    In operation, when one of the lobes is engaging the ground, the arbor is raised. As the grinder advances and the control wheel rolls along the ground, the control wheel is supported on a portion of its periphery transitioning between the maximum diameter of a lobe and the bottom of a depression on the control wheel. At this position, the arbor is lowered slightly to grind at a shallow depth in the pavement. Further advancement of the grinder and rotation of the control wheel takes the cutting assembly to a position in which one of the depressions of the control wheel engages the ground and the grinding arbor descends to its greatest depth into the pavement. This forms the bottom of a depression in the pavement of a sonic noise alert pattern. As the grinder advances further and the control wheel continues to roll along the ground, the cutting assembly again attains an intermediate position between fully raised and fully lowered. Further advancement moves the control wheel and arbor to a configuration with the next lobe contacting the pavement and the arbor raised. As the grinder advances, the pattern repeats and an evenly spaced sinusoidal pattern is formed in the pavement. The transitions between the pavement surface and the bottom of a depression formed in the pavement are gradual and the sinusoidal pattern formed is quieter when driven over by vehicle tires as compared to conventional sonic noise alert patterns. 
         [0018]    These features of novelty and various other advantages which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    Referring now to the drawings, wherein like reference numerals and letters indicate corresponding structure throughout the several views: 
           [0020]      FIG. 1  is a side elevational view of a pavement grinder according to the principles of the present invention; 
           [0021]      FIG. 2  is a bottom view of the rear of the truck chassis and cutting assembly with the laterally adjusted positions of the arbor shown in phantom; 
           [0022]      FIG. 3  is a side elevational view of a control wheel and grinding arbor in a first position for the pavement grinder shown in  FIG. 1 ; 
           [0023]      FIG. 4  is a side elevational view of a control wheel and grinding arbor in a second position; 
           [0024]      FIG. 5  is a side elevational view of a control wheel and grinding arbor in a third position; 
           [0025]      FIG. 6  is a top plan of a cutting head; 
           [0026]      FIG. 7  is a perspective view of the control wheel assembly; 
           [0027]      FIG. 8  is an end profile of the control wheel assembly; 
           [0028]      FIG. 9  is a side elevational view of a rim and tire for the control wheel assembly; and 
           [0029]      FIG. 10  is a side view of a sinusoidal profile of a sonic noise alert pattern made according to the principles of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0030]    Referring to the drawings and in particular to  FIG. 1 , there is shown a pavement grinder, generally designated  100 . The grinder  100  includes a truck chassis  102  supporting a cutting assembly  120  at the rear of the chassis  102 . The cutting assembly  120  has a grinding carriage  130  with an arbor  122 . As shown in  FIG. 6 , hardened carbide cutting teeth  124  mount in a side by side arrangement on an arbor axle  126 . The truck chassis  102  includes a cab  104  for the driver providing an open field of vision for the driver. The cab  104  also has controls for the grinder, such as speed and grinding functions. The truck chassis  102  provides propulsion and is powered by an engine  110 . An engine  118  mounted on the bed of the truck chassis  102  supplies power for hydraulic motors for the cutting assembly  120  and other systems of the cutting assembly  120 . A water tank  116  supplies the water for cooling and dust control. Moreover, oil and fuel tanks  114  may be mounted on the truck chassis. Moreover, although shown mounted to the rear of a truck chassis  102  in  FIG. 1 , the present invention may be configured as a dedicated self-propelled grinder. 
         [0031]    The cutting assembly  120  includes an arbor  122 , shown in  FIG. 6 , which includes cutting elements  124 , such as carbide cutting teeth, mounted along a cylinder  126  of the arbor  122 . The width of depressions ground in the pavement is variable depending on the number of teeth  124  and their arrangement on the arbor  122 . It can be appreciated that the teeth  124  may be mounted in groups or rows as may be best suited for the pavement material and the grinding conditions. The arbor  122  mounts to the grinding carriage  130  of the cutting assembly  120 . The grinding carriage  130  includes a housing  134  containing motors and a drive train, such as a drive belt(s) or drive chain(s) to drive the arbor  122 . The drive train may include belts, chains or motors directly mounted to the arbor shaft  126 . The cutting assembly may also include a cooling system typically providing cooling water for the arbor  122  to prevent the teeth  124  from overheating. The grinding carriage  130  has a control wheel  150  that is coupled by a linkage  132  to the arbor  122  to control up and down motion of the arbor  122 , as explained hereinafter. The height of the arbor  122  relative to the control wheel  150  can be changed by extending or retracting an adjustable profile cylinder  138 . The profile cylinder adjusts the relative height of the arbor  122  and therefore the depth of the recesses being formed in the pavement. 
         [0032]    The grinding carriage  130  is mounted to the rear of the chassis  102  on a support assembly  136 . As shown in  FIG. 2 , the support assembly  136  provides for adjusting the lateral position of the grinding carriage  130  relative to the chassis  102 . With such adjustment the chassis  102  can be driven in a position on a road that minimizes traffic disruption, keeps the pavement grinder  100  in a safe path of travel, allows the driver to view the grinding carriage  130  operate and keeps the arbor  122  cutting a pattern at the correct location on the pavement. 
         [0033]    Referring to  FIGS. 7-9  the control wheel  150  is configured as a non-round wheel. As shown in  FIG. 7 , the wheel  150  is formed of an outer tire  152  mounted on an inner rim  154 . The tire  152  is a solid element and made of a hard compound having minimal to know compression even when subjected to the forces associated with pavement grinding. As shown in  FIG. 8  the periphery of the tire  152  is non-round and the diameter varies in a continuous undulating repeated pattern. The pattern is sinusoidal and wraps around the periphery of the tire  152 . The tire  152  forms three lobes  160  of maximum diameter. The lobes  160  alternate with depressions  162  of minimum diameter. The areas between the lobes and the depressions  162  gradually transition in the sinusoidal pattern. In the embodiment shown the diameter varies one quarter inch, between twelve and three-quarter inches at the depressions  162  and thirteen inches at the maximum height of the lobes  160 . The distance between adjacent depressions  162  and also between the peaks of the lobes  160 , is fourteen and one-half inches. As the depressions  162  and the lobes  160  are evenly spaced about the periphery of the tire  152 , the distance between any two lobes  160  and the distance between any two depressions is the same fourteen and one-half inches. 
         [0034]    As shown in  FIG. 7 , the control wheel  150  is supported on an axle  156  and hub  158 . Moreover, the control wheel may include multiple tires  152 , rims  154  and hubs  158  mounted in a side by side relationship along the axle  156 . Therefore, the control wheel  150  provides increased lateral contact with the pavement and less variation due to minor flaws and defects in the pavement. 
         [0035]    Referring to  FIGS. 3-5 , the control wheel  150  controls the up and down movement of the cutting assembly and the depth with which the arbor  122  grinds the pavement. The control wheel has a non-circular outer periphery, as shown in  FIG. 8 . The diameter of the control wheel  150  increases and decreases gradually and continuously around the wheel in an evenly spaced pattern. In the embodiment shown, the control wheel  150  has three lobes  160  of increased diameter alternating with three depressions  162  of decreased diameter. The outer periphery gradually transitions from the depressions  162  to the lobes  160 . The gradual increase and decrease follows a sinusoidal pattern extending around the periphery of the control wheel  150 . The varying diameter causes the axle at the axis of rotation of the control wheel  150  to rise and fall. The control wheel axis of rotation is at a maximum elevation relative to the ground when one of lobes  160  is in contact with the ground surface while the axis of rotation is at its lowest elevation when one of the depressions  162  engages the ground. The height of the axis of rotation relative to the ground rises and falls as the control wheel  150  ground engagement point transitions between the maximum at the apex of the lobes  160  and the trough at the bottom of the depressions  162  on the control wheel surface. 
         [0036]    As the cutting assembly  120  is coupled to the control wheel  150 , the height of the arbor rises and falls with the height of the axle of the control wheel  150 , the arbor  122  also rises and falls in a sinusoidal pattern. The rising and falling causes the arbor to grind a sinusoidal pattern. Such a sonic noise alert pattern is shown in  FIG. 10 . It can be appreciated that the depth of the pattern can be varied by varying the relative position of the arbor relative to the control wheel  150 . However, the depth may be set so that the arbor  122  does not grind when the lobes engage the ground. It can also be appreciated that the grinding is at its deepest when the depressions of the control wheel  150  engage the ground. 
         [0037]    As shown in  FIG. 3 , when one of the lobes is engaging the ground, the arbor  122  is raised. As the grinder  100  advances and the control wheel  150  rolls along the ground, the control wheel  150  is supported on a portion of its periphery transitioning between the maximum diameter of a lobe and the bottom of a depression, as shown in  FIG. 4 . At this position, the arbor  122  is lower slightly to grind at a shallow depth in the pavement. Further advancement of the grinder and rotation of the control wheel  150  takes the cutting assembly  120  to the position shown in  FIG. 5 . In  FIG. 5 , one of the depressions of the control wheel  150  engages the ground and the grinding arbor  122  descends to its greatest depth into the pavement. This forms the bottom of a depression in the pavement of a sonic noise alert pattern. As the grinder advances further and the control wheel  150  continues to roll along the ground, the cutting assembly again attains the configuration of  FIG. 4 . Further advancement moves the control wheel  150  and arbor  122  to the configuration shown in  FIG. 3 . As the grinder  100  advances, the pattern repeats and an evenly spaced sinusoidal pattern is formed as shown in  FIG. 10 . The transitions between the pavement surface and the bottom of a depression formed in the pavement are gradual and the sinusoidal pattern formed is quieter when driven over by vehicle tires as compared to conventional sonic noise alert patterns. 
         [0038]    It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and the changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.