Abstract:
An extendable screed has independent height and angle of attack adjustment for a lower extender frame. At least one post and cylinder assembly are used to couple the lower extender frame to an upper extender frame at a pin that allows rotation of the lower extender frame relative to the upper extender frame. A vertical adjuster uses a drive rod with a pivoting attachment at the lower extender frame. An axis of rotation of the pin and an axis of rotation of the pivoting attachment are co-linear. This arrangement allows lower extender frame to move vertically while allowing angle of attack adjustments to be made about the co-linear axes of rotation. Simple screw adjusters displaced from the axis of the pin and collet assemblies allow raising and lowering the back of the lower extender frame to adjust the angle of attack.

Description:
TECHNICAL FIELD 
     The present disclosure relates paving systems and more particularly to a height and angle of attack adjusting system for a screed extension. 
     BACKGROUND 
     Paving systems use screeds to heat and compress paving materials, particularly asphalt paving materials. A screed of a paver may be adjustable out to six meters, but often it is desirable to extend the width through the use of extendable screeds. These extensions may add an additional 2 meters on either side of the main screed, for example, using hydraulically adjustable extendable screeds. 
     The extendable screeds may be mounted to the main screed body, but for various reasons are not usually collinear with the main screed body. For example, the extendable screeds may be mounted behind the main screed. Therefore, when the height of the main screed body is adjusted up or down, or its angle of attack is changed, the extension may move differently than the main body because it has a different radius from a pivot point of the main screed body. Angle of attack is the front-to-back angle of a screed that affects the difference in height above the paving surface of the front of the screed vs. the back of the screed. 
     Many current systems use a ‘four post’ system for adjusting the height and angle of attack of an extendable screed. However, manually loosening each post, making the adjustment, and re-tightening each post is very time and labor intensive. Other systems may allow the trailing edge of the extendable screed to be manually adjusted, but like the four post system, six or more individual bolts with locking nuts may need to be adjusted to make a change. Both of these adjustment techniques are time consuming and, given the work environment, often hot, dirty, and difficult to work on. 
     U.S. Pat. No. 6,158,921 discloses a screed extension mounted in front of a main screed body so that a rear-facing side of the extension touches a front-facing side of the main screed body. The distance of the extension from the main body determines where the contact between the two occurs and therefore, the angle of attack of the extendable screed. While the &#39;921 patent discloses both height adjustment and angle of attack adjustment, the angle of attack is directly a function of its height and requires fore-and-aft adjustment for each change in height. The &#39;921 patent does not disclose an extendable screed adjustment system that allows independent height and angle of attack adjustment. 
     SUMMARY 
     According to one aspect of the disclosure, an adjustment apparatus for adjusting an extendable screed relative to a main screed includes an upper extender frame coupled to one or more extend tubes of the main screed, a height tube coupled to the upper extender frame and a post movably inserted in the height tube. The adjustment apparatus may further include a first bracket attached to a lower portion of the post. The first bracket may be welded or otherwise attached to the post. The first bracket may include an ear attached to the bottom of the first bracket, for example, the ear may be welded to the bottom of the first bracket. The adjustment apparatus may also include a lower extender frame having a bulkhead plate that is proximate to the ear. A pin disposed through the ear and the bulkhead plate couples the post to the lower extender frame and allows rotation of the lower extender frame about a longitudinal axis of the pin. 
     According to another aspect of the disclosure, a method of adjusting an extendable screed, having upper and lower extender frames, relative to a main screed includes vertically supporting the lower extender frame of the extendable screed with a drive rod. The drive rod may be used to raise and lower the lower extender frame. The drive rod may be coupled at a first rotatable coupling that attaches the lower extender frame to the drive rod. The method may also include laterally supporting the lower extender frame with a post rotatably coupled to the lower extender frame at a second rotatable coupling. The post may be disposed in a tube coupled to the upper extender frame. The drive rod may be configured to operate such that rotating or turning the drive rod may cause the lower extender frame to raise or lower vertically. The method may include configuring the lower extender frame to rotate the lower extender frame about the first and second rotatable couplings to change an angle of attack of the lower extender frame relative to the main screed. 
     In yet another aspect of the disclosure, an apparatus is discussed and described for adjusting a height and angle of attack of an extendable screed relative to a main screed in a paving machine. The apparatus includes an upper extender frame coupled to one or more extend tubes of the main screed, a height tube coupled to the upper extender frame, a post movably inserted in the height tube and a first bracket attached to a lower portion of the post. The first bracket may include an ear. The apparatus may include a lower extender frame having a bulkhead plate proximate to the ear and a pin disposed through the ear and the bulkhead plate. The pin may couple the post and first bracket to the lower extender frame to allow rotation of the lower extender frame about a longitudinal axis of the pin. At least one elongate member may be coupled between the first bracket and the lower extender frame and may be displaced from the longitudinal axis of the pin. The at least one elongate member may be configured to extend and retract to set an angle of attack via rotation of the lower extender frame with respect to the upper extender frame about the longitudinal axis of the pin. The apparatus may also include a vertical adjuster that may in itself include a drive rod, a bearing housing trunnion mount coupled to the upper extender frame and configured turn the drive rod, and a trunnion block-lift attached to the drive rod and the lower extender frame configured to be raised and lowered relative to the bearing housing trunnion mount by turning the drive rod. 
     These and other benefits will become apparent from the specification, the drawings and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a screed assembly including an extendable screed mounted to a main screed; 
         FIG. 2  is a perspective view of a height adjustment system for an extendable screed; 
         FIG. 3  is a cutaway view of a portion of the lower extender frame and height tube of  FIG. 2 ; and 
         FIG. 4  is a flowchart of a method of adjusting the height and angle of attack of an extendable screed. 
     
    
    
     DESCRIPTION 
       FIG. 1  is a perspective view of a screed assembly  100  including an extendable screed  102  mounted to a main screed  104  of a paving machine. The extendable screed  102  may be attached to the main screed  104  via an upper extender frame  106  attached to one or more extend tubes  108 . The extendable screed  102  may be hydraulically extended and retracted to provide the desired additional width. Because the extendable screed  102  is behind the main screed  104  it often needs to be separately adjusted relative to the main screed  104  so that the resulting asphalt mat is uniform. To accomplish this, a lower extender frame  110  of the extendable screed  102  may be adjusted for height and angle of attack relative to the main screed  104  using an adjustment apparatus  140 , described in more detail with respect to  FIG. 2 . 
     The embodiment illustrated describes an extendable screed  102  that may be laterally adjusted via a hydraulic piston. It should be understood that the drawing of  FIG. 1  shows only one side of the screed assembly  100  and that most embodiments will have a complementary arrangement on the opposite side of the main screed  104 . In yet other embodiments, increasing the width of the screed assembly  100  may be accomplished by bolt-on extension screeds (not depicted). In an alternative embodiment, the bolt-on extension screeds may be coupled to the extendable screed  102 . It is anticipated that the height and angle of attack adjustment of the lower extender frame  110  disclosed below applies equally whether the extendable screed includes a bolt-on extension or not. 
     A person of ordinary skill in the art will appreciate that the entire apparatus is more complex than the illustration shown and that for simplicity in developing this disclosure, many parts unrelated to the operation of the adjustment apparatus  140  are not shown. 
       FIG. 2  illustrates an embodiment of an adjustment apparatus  140 . The adjustment apparatus  140  includes elements directly attached to the upper extender frame  106  and elements attached to the lower extender frame  110 . The upper extender frame  106  is not shown in  FIG. 2 . 
     One of the components attached to the upper extender frame  106  may be a height tube  120  welded or otherwise attached to the upper extender frame  106 . 
     Also attached to the upper extender frame  106  is a vertical adjuster including one or more bearing housing trunnion mounts  142  with associated drive rods  144 . As shown in the exemplary embodiment of  FIG. 2 , a belt or chain  150 , may be driven by a drive mechanism  148  using a motor or crank (not depicted). A tensioner  152  may be used to absorb slack in a known manner. The bearing housing trunnion mount  142  may include a gear mechanism that turns the drive rods  144  depending on the direction of travel of the belt  150 . In an embodiment, the drive rod  144  has a sprocket that engages the belt or chain  150 . In an embodiment, the drive rods  144  are threaded. As will be discussed further below, the drive rods  144  may engage one or more threaded trunnion block-lifts  146  that are coupled to the lower extender frame  110 , so that rotating or turning the drive rod  144  causes the trunnion block-lift  146  to raise and lower, and therefore causes the lower extender frame  110  to raise or lower relative to the main screed  104 . 
     The elements of the adjustment apparatus  140  attached to the lower extender frame  110  include the trunnion block-lift  146 . The trunnion block-lift  146  may be coupled to the lower extender frame  110  via a pin or bushing  154 . By attaching the trunnion block-lift  146  using the pin or bushing  154 , the lower extender frame  110  can rotate about the pin or bushing  154  in cooperation with the angle adjustment technique described below. Other components fixed to the lower extender frame  110  may also include a post  122  moveably inserted in the height tube  120  and a bracket  124  that is attached, for example, welded, to the post  122  below the height tube  120 . In an embodiment, the height tube  120  and post  122  may be cylindrical in shape. 
     The bracket  124  may include an ear  126  with a bore used to attach the bracket  124  to the lower extender frame  110  using a pin  128 . The pin  128  allows the lower extender frame  110  to rotate about the pin  128  relative to the bracket  124 , as discussed more below with respect to  FIG. 3 . 
     The bracket  124  may be oblong or rectangular in shape so that an angle adjuster  130  may be disposed at a distance from the pin  128 . The angle adjuster  130  may be a screw  132  or other elongate member that is, in an embodiment, fitted into a threaded hole  134  in the bracket  124  and coupled to the lower extender frame  110 . In an embodiment, as illustrated, the screw  132  may push down on the lower extender frame  110 , while a stud  136  may be fitted to the lower extender frame  110  and inserted through a hole in the bracket  124 . To adjust the angle of attack, the screw  132  may be turned to press down on the lower extender frame  110  and a nut  137  on the stud  136  may be turned to pull up on the lower extender frame  110 . Lock nuts or other fasteners or locks may be used to maintain the push/pull arrangement on the lower extender frame  110 . In many applications, once the angle of attack of the lower extender frame  110  is adjusted relative to the main screed  104 , it is rarely re-adjusted. 
     In other embodiments, the angle may be set by any other mechanism, such as a single screw with a ball-and-socket fitting (not depicted) on the lower extender frame  110 , a hydraulically-driven pin, etc. 
     As shown in the illustrated embodiment, an axis of rotation  155  of the trunnion block-lift  146  about a longitudinal axis of pin or bushing  154  is collinear with an axis of rotation  156  of the bracket  124  about a longitudinal axis of pin  128 . This allows the angle of attack of the lower extender frame  110  to be adjusted independently from the height setting. The bearing housing trunnion mount  142  may be mounted to the upper extender frame  106  with a pin or bushing  157  as a pivot point that allows at least a small amount of rotation between the adjustment apparatus  140  and the upper extender frame  106 , such as may occur during operation of the screed assembly  100 . A height indicator  158  attached to the post  122  may show a relative displacement between the extendable screed  102  and the main screed  104 . 
       FIG. 3  is a cutaway view of a portion of the lower extender frame  110  and height tube  120  of  FIG. 2 . As discussed above, the height tube  120  is fixed, e.g., welded, to the upper extender frame  106  while the post  122  and associated components connected below the post  122  are fixed to the lower extender frame  110 . The illustration shows the post  122  inserted into the height tube  120 . In the illustrated embodiment, one or more bushings  123  may be disposed between the height tube  120  and the post  122 . The bushings  123  may reduce the play between the height tube  120  and post  122  as these components carry a considerable side load when the paver is in operation.  FIG. 3  also shows the bracket  124  with ear  126 . In an embodiment, the ear  126  may be welded to the bracket  124 . The lower extender frame  110  may include a bulkhead plate  162  welded or otherwise formed or attached to the lower extender frame  110 . The bulkhead plate  162  may have a dynamic bore with a bushing  164 . By connecting the lower extender frame  110  to the bracket  124  using the pin  128 , the lower extender frame  110  is able to rotate relative to the bracket  124 . The bushing  164  may improve the ability to rotate the lower extender frame  110  about the pin  128 . In an embodiment, the bushing  164  may be heat treated to reduce wear. A collet  166  may be disposed between the pin  128  and the bracket  124  to lock the pin to the ear  126  of the bracket  124 . 
     INDUSTRIAL APPLICABILITY 
       FIG. 4  is a flowchart of a method  180  of adjusting the height and angle of attack of an extendable screed  102 . At a block  182 , the lower extender frame  110  may be vertically supported with one or more drive rods  144 . The drive rods  144  may be coupled at one end to the lower extender frame  110  at a trunnion block-lift  146 . As discussed above, the trunnion block-lift  146  may be rotatably coupled to the lower extender frame  110 . An opposite end of the drive rod  144  may be coupled to an upper extender frame  106  at a bearing housing trunnion mount  142 . The bearing housing trunnion mount  142  and its associated framework (not fully depicted) may be attached to one or more extend tubes  108  of the main screed  104 . In other embodiments, the upper extender frame  106  may be directly attached to the main screed  104 . 
     At a block  184 , lower extender frame  110  may be laterally supported with a post  122  rotatably coupled to the lower extender frame  110 . The post  122  may be disposed in a height tube  120  that is coupled to the upper extender frame  106 . In an embodiment a bushing  123  may be disposed between the post  122  and the height tube  120 . In an embodiment, the rotatable coupling may use a pin  128  disposed between an ear  126  coupled to the post  122  and bulkhead plate  162  attached to the lower extender frame  110 . Various embodiments may also include a bracket  124 , as described above. 
     At a block  186 , the one or more drive rods  144  may be configured to raise or lower the lower extender frame  110 . For example, the drive rods  144  may be threaded so that when the drive rods turn they cause a threaded trunnion block-lift  146  to move on the drive rod  144 . Because the trunnion block-lift  146  is attached to the lower extender frame  110 , as the trunnion block-lift  146  moves on the drive rod  144 , the lower extender frame  110  moves also. 
     At a block  188 , the lower extender frame  110  may be configured to rotate about the first and second rotatable couplings to change an angle of attack of the lower extender frame  110  relative to the main screed  104 . In an embodiment, the angle of attack may be adjusted by extending a screw  132  or other elongate member that is fixed to the bracket  124 , that is itself attached to the post  122 . The screw  132  may contact the lower extender frame  110  to provide a pressure that holds the lower extender frame  110  down. A stud  136  may be used to provide a counter pressure to urge the lower extender frame  110  up and lock it in place against the screw  132 . 
     The height and angle adjustment apparatus and method described above provide a significant improvement over “four post” systems used on current extendable screeds because it eliminates the iterative adjustment of position at each post to achieve both the desired angle of attack and height. The current design, by placing an axis of rotation  155  of the height adjustment system  140  in line with an axis of rotation  156  of the angle of attack adjustment allows coordinated, but independent, control of both height and angle of attack. The post  122  and tube  120  arrangement provides the necessary support for the high lateral forces on the lower extender frame  110  during paving operations while allowing simple height adjustment. Similarly, the adjustment apparatus  140  provides an easy-to-operate mechanism for adjusting height of the lower extendable frame  110  relative to the main screed  104 . 
     In accordance with the provisions of the patent statutes and jurisprudence, exemplary configurations described above are considered to represent a preferred embodiment of the present disclosure. However, it should be noted that the present disclosure can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.