[0001] The present invention relates generally to asphalt paver screeds and more particularly to a height control arrangement for a strike-off plate for controlling the amount of asphalt material supplied to the main screed.
[0002] Asphalt paving machines have a hopper that receives hot asphalt paving material located at the front of the machine. A conveyor for delivers the paving material from the hopper to the rear of the machine and deposits the asphalt at the back of the paver onto the road surface being paved. An auger is located at the rear of the paver for distributing some of the asphalt material laterally to the sides of the road surface. The asphalt paver also includes a floating screed, which is pulled behind the auger, for smoothing out and compressing the asphalt to the desired road mat thickness. A pair of tow arms pulls the screed unit behind the auger. The tow arms have forward ends pivotally mounted to the sides of asphalt paver and rearward ends pivotally mounted to the screed.
[0003] Many modern screeds are provided with a pair of extendible screed units attached to a main screed unit. Each extendible screed unit is movable laterally to one side of the main screed unit in order to vary the width the road mat being laid by the paver. Some extendible screed units are mounted behind the main screed unit. However, front mounted extendible screed units have become popular due to certain advantages they afford over rear mounted extendible screed units. The front mounted screeds use a strike-off plate positioned in front of the extension units to limit the amount of paving material between the side extension units during retraction.
[0004] Screeds are provided with adjustments for controlling the “pitch” or “angle of attack” of the screed relative to the desired surface of the paving mat for controlling the depth of the mat being laid. For instance, raising the leading edge of the screed plate increases the angle of attack, thus increasing the depth of the mat being laid. However as the angle of attack is increased, the height of the strike-off plate of prior screeds also increased. Because such strike-off plate is mounted at a substantial distance ahead of the main screed in front of the screed extensions, the rise in height of the strike-off plate is disproportionately greater than the increase in the mat height being formed by the screed. This results in too much asphalt material being fed to the main screed and an undesirable build-up between the screed extensions. One prior design that addresses this problem is disclosed in U.S. Pat. No. 6,056,474 issued May 2, 2000 to David W. Nolan and is assigned to the owner of the present application.
[0005] The one aspect of the present invention a height control arrangement is provided for a strike-off plate of an asphalt paver screed assembly. The screed assembly has at least one main screed unit and at least one screed extension unit. The screed extension unit is mounted in front of the main screed unit and is laterally movable beyond one end of said main screed unit. The height control arrangement has the strike-off plate mounted in front of the main screed unit at a position ahead of the screed extension unit. An actuator is connected with the strike-off plate and a sensor is mounted behind the strike-off plate and in front of the main screed unit. The sensor is adapted for measuring an amount of material. A controller is connected to control the actuator responsive to the amount of material so as to adjust the height of the strike-off plate.
[0006] In yet another aspect of the present invention a method is provided for controlling the height of a strike off plate of an asphalt paver screed assembly. The screed assembly has at least one main screed unit and at least one screed extension unit mounted in front of said main screed unit. The method comprising the steps of sensing an amount of material built up behind said strike off plate and in front of said main screed unit and then adjusting the height of said strike off plate in responsive to the amount of material sensed.
[0007]
[0008]
[0009]
[0010]
[0011] Referring now to
[0012] The two main screed units
[0013] An adjustment mechanism
[0014] The screed assembly
[0015] A pair of strike-off plates
[0016] Referring to
[0017] In the embodiment shown, the support assembly
[0018] The support assembly
[0019] As seen in
[0020] Referring now to
[0021] In operation, the construction of the height control arrangement
[0022] Additionally it should be noted, the linkage mechanism
[0023] The primary advantage of the strike-off plate height control arrangement