AS2252C Asphalt Screed Caterpillar

Screed Extenders

Illustration 1	g01472087
Right screed extender (1) Extender cylinder (2) Extender (3) Walkway latch (4) Extend scale (5) Walkway

Screed extenders (2) are attached to the front of the main screed through a triangular support configuration. This structure provides torsional resistance and rigidity. The right extender is shown above.

Extenders move in and out in order to allow variable paving widths. Extenders can also be raised, lowered, and tilted in relation to the main screed. The screed width switches at the main operator stations for the screed and the extender operator stations, control the cylinders that extend and retract the extenders. Single hydraulic cylinder (1) is attached to each extender. The cylinder extends the extender and the cylinder retracts the extender. Scale (4) indicates the distance the extender is extended.

Each extender is equipped with folding walkway (5). Walkways allow the operator to move between operator control stations without walking on the mat. All walkways are mounted to the main screed. The extender walkways fold up against the side of the main screed. Each walkway is secured by latch (3) when the walkway is in the upright position.

Angle of Attack for the Extender (Adjustment)

Illustration 2	g01472088
Top center of screed extenders (1) Adjustment bolt

The angle of attack of each screed extender is adjustable. Turn adjustment bolt (1) clockwise in order to increase the angle of attack. Turn the adjustment bolt counterclockwise in order to decrease the angle of attack.

Extender Height

Illustration 3	g01472089
Top center of screed extenders (1) Extender height scale

The AS2252C screed is equipped with a power extender mechanism for control of the height of the extender. Scales indicate the height of the extenders. The extender height scales are located on the main screed. Left extender height scale (1) is shown in the image above.

The extenders can be lowered a distance of 64 ± 6 mm (2.5 ± 0.25 in) below the main screed. The extenders can be raised a distance of 25 ± 6 mm (1 ± 0.25 in) above the main screed. Extender height scale (1) shows the amount of adjustment in increments of 6 mm (0.25 in). At the initial setup, the extenders should be set a distance of 6 mm (0.25 in) lower than the main screed.

Illustration 4	g01472091
Left side of main screed (2) Height control motor for the extender

The extender height control motors are located on the main screed. Left extender height motor (2) is shown in the image above.

The height control mechanism for the extender uses electric motors to raise the extenders and the control lowers the extenders. The left operator station has a switch that operates electric motor (2) for the left extender. The right operator station has a switch that operates the electric motor for the right extender.

Extender Slope

Illustration 5	g01472092
Above walkway on right side of main screed (1) Extender slope scale

The AS2252C has a hydraulic slope mechanism that tilts the extenders in order to produce a slope in the mat. Slope scales indicate the percent of slope. Right slope scale (1) is shown above.

Note: Use the extender slope scale as a reference only. Measure the mat in order to determine the actual slope of the extender.

Illustration 6	g01472093
Center of main screed (2) Left extender slope cylinder (3) Right extender slope cylinder

The extender slope cylinders are mounted on the main screed. This location is near the center. Left slope cylinder (2) sets the slope of the left screed extender. Right slope cylinder (3) sets the slope of the right screed extender.

The slope cylinders are controlled by valves on the extender and slope manifold. Switches on the operator stations for the screed control the slope valves. The left slope is controlled by a switch on the left operator station for the screed. The right slope is controlled by a switch on the right operator station for the screed.

Illustration 7	g01472095
Center of main screed (4) Shutoff valve for the slope cylinder

Each slope cylinder has shutoff valve (4). The valve is mounted on the side of the cylinder. The shutoff valve for the left slope cylinder is shown in the image above.

When shutoff valve (4) is closed, the position of the cylinder is locked. Also, the slope control switches on the operator stations cannot change the slope angle. The shutoff valve can also control the speed of the cylinder. When the valve is partially closed, the motion of the cylinder is slower. If the cylinder reacts too quickly, the height of the screed extender may be affected.

Extender And Slope Manifolds

Illustration 8	g01472096
Top of main screed to left of center (1) Extend solenoid (left extender) (2) Slope increase solenoid (left extender) (3) Retract solenoid (left extender) (4) Slope decrease solenoid (left extender) (5) Left extender and slope manifold

There are two extender and slope manifolds on the screed. Left manifold (5) contains valves and solenoids that control the left extender cylinder and the left slope cylinder. The right manifold (next illustration) contains valves and solenoids that control the right extender cylinder and the right slope cylinder. The left extender and slope manifold is shown above.

Each valve on the left extender and slope manifold (5) contains two solenoids. The function of each solenoid can be determined by the designation (number and color) of the power supply wire. The wire designations and solenoid functions are in the following list:

• K845-OR wire (left extender extend (1) )

• H879-YL wire (left extender slope increase (2) )

• K841-BR wire (left extender retract (3) )

• H880-GN wire (left extender slope decrease (4) )

Illustration 9	g01472097
Top of main screed to right of center (6) Extend solenoid (right extender) (7) Slope increase solenoid (right extender) (8) Right extender and slope manifold (9) Retract solenoid (right extender) (10) Slope decrease solenoid (right extender)

The right extender and slope manifold (8) is shown in the illustration above. The right extender and slope manifold contains valves and solenoids that control the right extender cylinder and the right slope cylinder.

Each valve on the right extender and slope manifold (8) contains two solenoids. The function of each solenoid can be determined by the designation (number and color) of the power supply wire. The wire designations and solenoid functions are in the following list:

• K846-PK wire (right extender extend (6) )

• H881-GN wire (right extender slope increase (7) )

• K842-BU wire (right extender retract (9) )

• H882-WH wire (right extender slope decrease (10) )

Illustration 10	g01472099
Below right operator station on main screed (11) Return manifold

Return manifold (11) is located on top of the main screed and behind the right operator station.

Return manifold (11) receives return oil from the following systems: extender hydraulic system, slope hydraulic system and berm hydraulic system. Oil flows from the return manifold to the tank on the machine through a single line.

Berm System

Illustration 11	g01472101
Outboard edge of extender (1) Berm lock lift cable (2) Berm top bolt (3) Berm mechanism (4) Berm lock arm

Optional berm system (3) creates a tapered berm along the edge of the mat. Switches on the screed operator stations control the berm system. When the berm system is not active, the extender is held in the level position by lock arm (4) and bolt (2) .

To use the berm function, remove top bolt (2). Lock arm (4) will fall loose. The berm cylinder (not shown) can then be controlled by the berm switches on the operator stations for the screed.

To return the berm system to the locked position, first level the mechanism with the berm controls. Pull up cable (1) in order to lift up lock arm (4) into position. Then install bolt (2).

Illustration 12	g01472103
Outboard end of left extender (5) Left lower solenoid (6) Right lower solenoid (7) Right berm control valve (8) Left berm control valve (9) Left raise solenoid (10) Right raise solenoid (11) Berm manifold (12) Berm shutoff valve

The berm system includes a manifold (11) and a shutoff valve (12). Two control valves are mounted on the manifold. Control valve (7) controls the right berm cylinder, and control valve (8) controls the left berm cylinder. Each control valve has two solenoids in order to control up motion and control the down motion of the berm mechanism. The manifold and the shutoff valve are mounted on the left side of the main screed.

The function of each solenoid and the corresponding wire numbers are in the following list:

• 870-OR wire (left berm lower (5) )

• 872-OR wire (right berm lower (6) )

• 871-YL wire (left berm raise (9) )

• 873-YL wire (right berm raise (10) )

Strike off Plates

Illustration 13	g01472104
Front of screed (1) Strike off plates (2) Adjustment bolts

The leading edge of the screed is equipped with strike off plates (1). The adjustable strike off plates limit the amount of material that reaches the screed plate. Screed extenders have two strike off plates.

Each strike off plate (1) is equipped with two adjustment screws (2). These screws allow the operator to make fine adjustments to the position of the strike off plates in order to accommodate different mixes.

Strike off plates (1) are adjusted at the factory so that the bottom of the plate is approximately 19 mm (0.75 inch) higher than the bottom of the screed plate. The factory setting is appropriate for paving with mixes of average consistency. The strike off plates should be raised when the mix is sandy. The strike off plates should be lowered when the mix is coarse.

Screed Plates

Illustration 14	g01472105
Bottom surface of screed (1) Screed plate (2) Adjustment nuts

Each extender and the main screed are equipped with flat screed plate (1) with a formed curve at the front. Two checks can be made on the screed plate. The two checks are for thickness and flatness. A screed plate should be replaced if the thickness of the plate is less than 3.175 mm (0.125 inch).

The screed plate should be flat to within a measurement of 0.76 mm (0.030 inch) along the following locations: front edge, rear edge and diagonal line. If a screed plate is not flat along the following locations, adjustment nuts (2) can be used to adjust the front and rear edges of the screed plate: front edge, rear edge and diagonal line.

Note: The screed should be in the null position with no crown before any flatness checks are made.

End Gates

Illustration 15	g01472106
Outboard end of screed extender (1) End gate (2) Jacks (3) Guide bolts (4) Springs (5) Jack handles

The screed is equipped with one spring loaded end gate (1). The end gates are located outboard of either extender. The end gates prevent material from flowing around the screed and the end gates create the longitudinal joint during paving.

Two spring loaded jacks (2) control the height of each end gate. Jack handles (5) are permanently attached to each jack. When a jack is rotated clockwise, the corresponding side of the end gate lowers and the spring force increases. Also, the available vertical travel decreases. When a jack is rotated counterclockwise, the corresponding side of the end gate rises and the spring force decreases. Also, the available vertical travel increases. Guide bolts (3) allow the end gate to travel vertically and the guide bolts allow the end gate to follow the profile of the surface that is being paved. Springs (4) keep gate (1) in contact with the surface.

Springs (4) should always be adjusted so that there is sufficient movement in order to allow the end plate to follow the profile of the surface that is being paved. If the springs are not properly adjusted, the screed may ride on the end gate. As a result, there will be increased wear on the end gate and possible quality problems with the mat.

When the initial lift is laid, adjust the end gate in order to ride on the grade. Adjust the end gate to ride on the adjacent mat in order to match a longitudinal joint.

Illustration 16	g01472107
Top of end gates (5) Jack handle (6) Detent lock

Jack handles (5) on the end gates include a feature that allows the jacks to swivel back over the end gate. This feature will also allow the jack handles to be flush against the end gate. These positions are used when the jacks are not being used.

In order to reposition jack handle (5), the operator must pull the handle out of detent lock (6). The operator must then twist the handle to the desired position. When the operator releases the handle, the detent mechanism will engage and the handle will remain in position.

Adjustment Bolts for the Walkway

Illustration 17	g01472108
Back of screed (1) Adjustment bolts

Adjustment bolts (1) are attached to the frame of the screed and below the pivot points of the walkway supports. Extensions on the walkway supports rest on the head of the bolts. As the bolts move out, the back edge of the walkway rises. The bolts allow the operator to level the walkways and the bolts allow the operator to keep the walkways level as the screed wears.

Vibratory system

Illustration 18	g01472109
Right side of main screed (1) Vibratory motor

The screed is equipped with a vibratory system that includes four vibratory motors (1). The motor in the right half of the main screed is shown in the image above. One motor is located in the right side of the main screed and one motor is located in the left side of the main screed. Each screed extender is also equipped with one vibratory motor. The vibratory motors on the left side of the machine are connected in series. The vibratory motors on the right side of the machine are also connected in series.

Each motor turns a shaft that holds eccentric weights. As the shaft turns, the eccentric weights cause vibration. The vibration aids in the initial compaction of the mat.

Illustration 19	g01472110
Top of Screed and behind left operator station (2) Flow divider (vibratory hydraulic system)

Flow divider (2) is located behind the left operator station on the main screed. The flow divider receives oil from the vibratory pressure line that connects directly to the tractor.

Flow divider (2) sends equal amounts of hydraulic oil to the vibratory motors on the left side of the screed and to the vibratory motors on the right side of the screed. Since the vibratory motors on the left side of the screed are connected in series, and the vibratory motors on the right side of the screed are connected in series, all four motors turn at the same speed. Return oil from the vibratory motors flows to the return manifold on the screed. Case drain oil from the vibratory motors flows through a separate line. This oil flows directly back to the machine.