US20170073907A1

US20170073907A1 - Screed cushioning system and method

Info

Publication number: US20170073907A1
Application number: US14/850,293
Authority: US
Inventors: Todd Jennings
Original assignee: Caterpillar Paving Products Inc
Current assignee: Caterpillar Paving Products Inc
Priority date: 2015-09-10
Filing date: 2015-09-10
Publication date: 2017-03-16
Also published as: CN206090252U; DE202016105016U1

Abstract

A paver including a screed and a hydraulic actuator coupled to the screed. The hydraulic actuator is configured to raise the screed to a transport position by pressurizing a raise end of the hydraulic actuator. An accumulator is selectively connected to the hydraulic actuator. A control valve configured to switch the screed in the transport position between a non-cushioned state and a cushioned state by connecting the accumulator to the raise end of the hydraulic actuator in the cushioned state. The hydraulic pressure of the accumulator is equalized to a hydraulic pressure of the hydraulic actuator before the control valve switches the screed from the non-cushioned state to the cushioned state.

Description

TECHNICAL FIELD

The present disclosure relates generally to a paving machine. In particular, the present disclosure relates to a cushioning system for a screed of a paving machine.

BACKGROUND

A paving machine, commonly known as a paver, is used in combination with a screed to lay a paved surface, also referred to as a mat or paving mat. A paving machine is generally a self-propelled machine designed to receive, convey, distribute, and compact paving material, such as asphalt, to create a flat, consistent surface over which vehicles may travel. A paving machine typically has a tractor with a hopper at its front end for receiving paving material. A conveyor system on the machine transfers the paving material from the hopper towards a screed mounted rearwards of the tractor. Screw augers positioned behind the tractor and in front of the screed assist in moving the paving material so that a relatively uniform volume of paving material is distributed in front the screed.
The screed is a heavy assembly towed behind the paving machine by a pair tow arms for smoothing out and compacting the paving material distributed by the screw augers. When the paving machine moves, the screed physically levels any paving material lying higher than a predetermined height above the roadway surface, leaving a generally uniform thickness of the paving material. The screed also compacts the paving material in order to provide a uniform, smooth, durable pavement surface.
The screed is generally connected to the frame of the paving machine by tow arms. These tow arms have one end coupled to the frame of the machine and the other end coupled to the screed. Typically, hydraulic actuators are coupled to the screed or the tow arms in order to raise or lower the screed relative to the surface being paved. When the paving machine is engaged in paving a mat on a desired surface, the paving machine travels at a very slow speed with the screed floating above the ground surface in order to provide a mat of a specified thickness and to level and compact the material being paved. For travelling or transportation of the paving machine while the machine is not engaged in paving, the screed is raised to a higher or a transport position in order to avoid the screed from hitting the ground surface or objects lying on the ground. While moving, the screed may bounce or there may be unwanted movements in the screed due to uneven road conditions or due to other forces acting on the screed. The weight of the screed causes these movements to be transmitted back to the main body of the paver, resulting in imbalance of the paver and difficulty in handling the paver while travelling. These movements may also deteriorate the ride quality of the paver. Also, the bouncing screed may damage the paved surface.
U.S. Pat. No. 5,556,227 discloses providing an elastic support for a screed of a paver. The paver uses an accumulator to damp the movement of screed by providing an accumulator connected to the lifting cylinder when the paver is travelling. When such cushioning systems are switched on, there may be some unwanted movements in the screed or unevenness in switching the screed to the cushioned state. The sudden shift from a normal raised position to a cushioned state may lead to sudden downward motion of the screed. This motion may lead to a momentary feel of an unstable paver.

SUMMARY OF THE INVENTION

The present disclosure provides for a paver including a screed, an actuator coupled to the screed and configured to raise the screed to a transport position by pressurizing a raise end of the actuator. An accumulator is selectively connected to the actuator. A control valve is configured to switch the screed in the transport position between a non-cushioned state and a cushioned state by connecting the accumulator to the raise end of the actuator in the cushioned state. The accumulator hydraulic pressure is equalized to actuator hydraulic pressure before the control valve switches the screed from the non-cushioned state to the cushioned state.
The present disclosure further provides for a paver including a screed, an actuator coupled to the screed and configured to move the screed between a raised position and a lowered position. The paver further includes a control valve configured to switch the screed between a non-cushioned state and a cushioned state in the raised position. A controller is configured to raise the screed to the raised position and switch the screed to a cushioned state when the screed is in the raised position.
The present disclosure provides for a method of cushioning a screed. The method includes raising the screed from a lowered position to a raised position. The method further includes equalizing an actuator pressure to an accumulator pressure and placing the screed in a cushioned state by connecting the actuator to the accumulator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a paver in accordance with an embodiment.

FIG. 2 illustrates a schematic diagram of a paver with the screed in a raised position.

FIG. 3 illustrates a schematic diagram of a hydraulic circuit in accordance with an embodiment.

FIG. 4 illustrates a schematic diagram of a hydraulic circuit in accordance with an embodiment.

FIG. 5 illustrates a schematic diagram of a hydraulic circuit in accordance with an embodiment.

FIG. 6 illustrates a method of operating a paver 10 in accordance with an embodiment.

DETAILED DESCRIPTION

FIG. 1 illustrates a paver 10. The paver 10 has a body 12, a frame 14, ground engaging means 16, a power source 18 and a screed control system 100. The paver 10 further has a screed 20 towed behind the body 12 by tow arms 22 attached to the frame 14 of the paver 10. Tow arms 22 are on both sides of the paver 10. Each tow arm 22, at a first end 24 is coupled to the frame 14, and at a second end 26 is coupled to the screed 20.
Actuators 30 are coupled to the screed 20 and the frame 14. As one of skilled in the art will appreciate, the actuators 30 may be any type of structure or mechanism responsible for moving a component. For example, the actuators 30 may be hydraulic or pneumatic actuators. In the embodiment illustrated in FIG. 1, the actuators 30 are hydraulic actuators and are coupled to the screed 20 via tow arms 22 on each side of the paver 10. Actuators 30 may be hydraulic cylinders with a rod end 34 and a head end 32. The head end 32 of each actuator 30 is coupled to the frame 14 and the rod end 34 of the actuator 30 is coupled to tow arms 22. Due to the connection of the actuators 30 to the tow arms 22, actuation of the actuators 30 leads to raising or lowering the screed 20.
FIG. 1 illustrates the screed 20 in a lowered position. During paving operations, the screed 20 is kept in a lowered position such that the screed 20 floats on a surface 8 being paved. In lowered position, the screed 20 is kept very close to the surface 8 to level and compact the paving material and provide a mat of certain thickness on the surface 8. When paver 10 is not engaged in paving, the screed 20 may be kept in a raised position or a transport position. The raised or transport position may be a fully raised or partly raised position and may be at a predetermined height above the surface 8 being paved. FIG. 2 illustrates the screed 20 in a raised position. While travelling the screed 20 may bounce due to uneven road conditions. In raised position, the screed 20 is raised to a sufficient height that ensures the screed 20 does not hit the surface 8 or obstruct the travel of the paver 10 by hitting other objects lying on the surface 8.
The paver 10 may include a position detection device 40 operatively connected to the actuator 30 to detect the position of the screed 20. In the illustrated embodiment, position detection device 40 is coupled to the actuator 30 and is configured to detect the position of the screed 20 based on the position of the actuator 30. In an alternate embodiment, the position detection device 40 may be configured to detect the position of the screed 20 based on the position of the tow arms 22.
The paver 10 further includes a locking system 50 to lock the screed 20 in a transport position or raised position. FIG. 1 illustrates the locking system 50 that includes a stop member 52 to restrict or lock travel of the screed 20 once the screed 20 is raised. In alternate embodiments, the stop member 52 may be configured to restrict or lock travel of the screed 20 out of the transport position when the screed 20 is in the cushioned state. The stop member 52 may be actuated by any mechanism known in the art. For example, the stop member 52 can be actuated either hydraulically or electrically. The locking system 50 may be any of the locking arrangements known in the art. One such arrangement may include a stop member 52 that when extended blocks the downward travel of the tow arms 22 beyond a certain position, when the screed 20 is raised to a transport position or above a certain predetermined height.
FIG. 3 illustrates a schematic diagram of a hydraulic circuit used in the screed control system 100 for cushioning the screed 20 in accordance with the present disclosure. FIG. 3 depicts a control module 200, a cushioning system 300 and a damping system 400. Further, FIG. 3 illustrates two actuators 30 and two rod end valves 130. The two actuators 30 are used for raising or lowering the screed 20. The actuators 30 have a rod end 34 and a head end 32. In the illustrated embodiment, the rod end 34 works as a raise end for raising the screed 20. Pressurizing the rod end 34 of the actuator 30 leads to raising the screed 20. In an alternate embodiment, the head end 32 may be configured to work as a raise end.
A head end conduit 102 connects the head end 32 of the actuators 30 to the control module 200. A rod end conduit 104 connects the rod end 34 of the actuators 30 to the damping system 400, the cushioning system 300 and the control module 200. Two rod end valves 130 are connected between the rod end 34 and the damping system 400 for controlling the flow of fluid to and from the rod ends 34 of the actuators 30.
Referring to FIG. 3, the control module 200 has a pump conduit 212 connected to a pump 210 and a tank conduit 222 connected to a tank 220. The pump conduit 212 and the tank conduit 222 are connected to a proportional pressure reducing or relieving valve 230. The proportional pressure reducing valve 230 selectively connects the pump 210 and the tank 220 to the hydraulic circuit to maintain desired pressure at an outlet of proportional pressure reducing valve 230. In the embodiment illustrated, the proportional pressure reducing valve 230 is a three way two position valve. Any proportional pressure reducing mechanism known in the art can be used for this function. The proportional pressure reducing valve 230 may be controlled by an operator or a controller 500. In the embodiment as illustrated, the pump conduit 212 is directly connected to the proportional pressure reducing valve 230, whereas the tank conduit 222 is connected to the proportional pressure reducing valve 230 via a stop valve 240. The stop valve 240 is configured to block or allow the flow of hydraulic fluid towards the tank 220. A pressure relief mechanism 250 is connected in parallel to the stop valve 240 between the proportional pressure reducing valve 230 and the tank 220. Pressure relief mechanism 250 allows selection of two working ranges of proportional pressure reducing valve 230. When the stop valve 240 is open, working range is zero to maximum of the proportional pressure reducing valve 230. When the stop valve 240 is closed, working range is from the setting of the pressure relief mechanism 250 to sum of the pressure setting of pressure relief mechanism 250 and the maximum setting of the proportional pressure reducing valve 230. Any pressure relief mechanism known in the art can be used for this function.
The control module 200 further includes a first valve 260 and a second valve 270. The first valve 260 and the second valve 270 regulate the flow of hydraulic fluid to and from the head end conduit 102 and the rod end conduit 104, respectively. Proportional pressure reducing valve 230 is connected to the first valve 260 and the second valve 270. The first valve 260 and the second valve 270 work in tandem with the proportional pressure reducing valve 230, the stop valve 240 and the rod end valves 130 to control the raising or lowering of the screed 20. Tank 220 is connected to the first valve 260 and the second valve 270 via a parallel tank conduit 224, in order to receive hydraulic fluid from the head end conduit 102 or the rod end conduit 104. The first valve 260 is connected to the head end 32 via the head end conduit 102, and the second valve 270 is connected to the rod end 34, rod end valves 130 and the cushioning system 300 via rod end conduit 104. Pressure sensors 60 may be connected to the hydraulic circuit to measure pressure in the hydraulic circuit. The pressure sensor output may be used to provide signal or feedback to the controller 500, in order to provide closed loop control of system pressure. The pressure sensor feedback may also be used to maintain cushioned state.
Further, a damping system 400 is connected to the rod end conduit 104. The damping system 400 includes a damping orifice 410 and a one way check valve 420. The damping orifice 410 damps the downward motion of the screed 20 by restricting the free flow of hydraulic fluid from the rod end 34 of the actuator 30. Whereas, the check valve 420 allows for free flow of hydraulic fluid towards the rod end 34 for raising the screed 20. In the embodiment illustrated, the damping system 400 includes a set of a check valve 420 and a damping orifice 410 connected in parallel, to the rod end 34 of each actuator 30.
FIG. 3 further depicts the cushioning system 300 in accordance with an embodiment. The cushioning system 300 includes a control valve 350 that transitions the screed 20 from a cushioned state to a non-cushioned state. In the cushioned state, the control valve 350 connects an accumulator 330 to the rod end 34 of the actuator 30. In the embodiment illustrated, the control valve 350 includes a pair of valves 310,320 that work in tandem to stop or allow the fluid flow between the rod end 34 and the control module 200, and to allow or stop the fluid flow between the rod end 34 and the accumulator 330. A cut-off valve 310 controls the fluid flow between the rod end 34 and the control module 200 by either blocking or allowing fluid flow. Similarly, an accumulator valve 320 controls the fluid flow between the rod end 34 and the accumulator 330 by either blocking or allowing fluid flow.
For switching the screed 20 to the cushioned state, the cut-off valve 310 is switched to block the flow of fluid between the rod end 34 and the control module 200, and the rod end valves 130 and the accumulator valve 320 are switched to connect the accumulator 330 to the rod end 34. Whereas, for switching the screed 20 to a non-cushioned state, the cut-off valve 310 is switched to allow the flow of fluid between the rod end 34 and the control module 200, and the rod end valves 130 and the accumulator valve 320 are switched to disconnect the accumulator 330 from the rod end 34.
In the embodiment as illustrated in FIG. 3, the cut-off valve 310 and the accumulator valve 320 are shown as two separate valves. In an alternate embodiment, the function of the accumulator valve 320 and the cut-off valve 310 may be incorporated in a single control valve.
Further, a pressure equalization passage 340 connects the rod end 34 of the actuator 30 to the accumulator 330. The pressure equalization passage 340 while restricting any substantial flow of fluid between the rod end 34 and the accumulator 330, ensures that the pressure in the rod end 34 and the accumulator 330 are equalized. Thus, when the screed 20 is switched to the cushioned state from a non-cushioned state, the transition can take place smoothly as there is no pressure equalization needed at the time of the transition. Similarly, due to the pressure equalization passage 340, the transition of the screed 20 from a non-cushioned state to a cushioned state can also take place smoothly due to pressure equalization between the accumulator 330 and the rod end 34 of the actuators 30. In other embodiments, alternate pressure equalization mechanisms known in the art such as using pressure sensors and valve actuation may be used to match actuator pressure to the accumulator pressure.
A controller 500 is connected to the hydraulic circuit and is configured to control various modules, valves and devices in the hydraulic circuit in order to perform the operation of the screed control system 100. The controller 500 may include a single microprocessor or multiple microprocessors that include a means for controlling an operation of various systems and valves in the hydraulic circuit. Commercially available microprocessors can be configured to perform the functions of the controller 500. The controller 500 may include a memory, a secondary storage device, a processor, and other components for running an application. Various other electrical or electronic circuits may be associated with the controller 500 such as power supply circuitry, signal conditioning circuitry, solenoid driver circuitry, and other types of circuitry. Additionally, there may be several measuring and monitoring devices, for example pressure sensors, position sensors or motion sensors, coupled to different parts of the screed control system 100 and the controller 500 to sense various parameters needed in order to effectively control the screed control system 100.
The controller 500 ensures that the valves of the screed control system 100 work in tandem to achieve different positions of the screed 20. The controller 500 generates signals to switch the various valves in different positions in order to control the raising, lowering, cushioning or locking of the screed 20.
The controller 500 may be coupled to the position detection device 40 for detecting the position of the screed 20. Further, the controller 500 may be configured to determine whether the screed 20 is in a cushioned state or a non-cushioned state. The controller 500 may be configured to determine the screed 20 in a transport position or above a certain predetermined height and automatically engage the cushioned state. Further, the controller 500 may be configured to automatically lock the screed 20 in the transport position when the screed 20 is in a cushioned state.
The screed control system 100 operates as follows. The controller 500 may be configured to generate signals for actuation of the various valves in the required positions for effecting different operations on the screed 20. FIG. 3 shows an arrangement for raising the screed 20 to a transport position. Referring to FIG. 3, the pump conduit 212 receives fluid from the pump 210 and the fluid is then passed through the proportional pressure reducing valve 230 and the second valve 270. Further, the fluid passes from the cut-off valve 310 and the damping system 400 towards the rod end valves 130. Finally, the fluid then enters the rod end 34 of the actuator 30. The pressurization of the rod end 34 thus results in raising of the screed 20. The fluid in the head end 32 exits and passes through the first valve 260 and is supplied to the tank 220 through the parallel tank conduit 224.
FIG. 4 depicts the screed control system 100 with same elements as in FIG. 3, with the change in position of different valves of the hydraulic circuit to depict the fluid flow path during lowering of the screed 20. Referring to FIG. 4, the fluid received from the pump 210 flows through the proportional pressure reducing valve 230 and then passes through the first valve 260 towards the head end 32 of the actuator 30. The pressurized fluid from the pump 210 pushes the piston 31 of the actuator 30 down. Consequently, fluid from the rod end conduit 104 exits and passes through the rod end valves 130 and the damping orifice 410. Further, the fluid passes through the cut-off valve 310 and then flows towards the tank 220 via the second valve 270.
In the embodiment in accordance with FIG. 4, the screed 20 is lowered using pressurized fluid from the pump 210. In an alternate embodiment, the screed 20 may lower under its own weight. In accordance with the alternate embodiment the rod end 34 and the head end 32 of the actuator 30 may both be connected to the tank 220. As discussed above, the damping system 400 damps the downward movement of the screed 20 to avoid a sudden downward motion or fall of screed 20.
FIG. 5 depicts the arrangement of the screed control system 100 when the screed 20 is switched to a cushioned state. Referring to FIG. 5, the rod end valves 130 allow for fluid communication between the rod end 34 and the damping system 400. In the cushioned state, the rod end conduit 104 is disconnected with the control module 200 using the cut-off valve 310. The accumulator valve 320 is switched to a position that connects the rod ends 34 to the accumulator 330. The accumulator 330 is configured to absorb the pressure fluctuations in the rod end 34 caused by movements in the screed 20 while the screed 20 is in a transport position.
When the screed 20 is switched to a cushioned state there is no difference in pressure in the rod end 34 and the accumulator 330, as the pressure equalization passage 340 equalizes the hydraulic pressure of the accumulator 330 with the current hydraulic pressure of the actuator 30 at the rod end 34. This enables smooth transition of the screed 20 from the non-cushioned state to a cushioned state.
In accordance with an embodiment, the controller 500 may be configured to automatically switch the screed 20 into a cushioned state on detecting the transport position or raised position of the screed 20. The controller 500 may further engage the locking system 50 to automatically switch or move the stop member 52 to an operating position when the screed 20 is determined in a transport position or in a cushioned state. In an embodiment, the controller 500 may move the stop member 52 based on an operator input.
In an alternate embodiment, when the screed 20 is switched to a cushioned state, the controller 500 may be configured to raise the screed 20 to a transport position, engage the screed 20 to a cushioned state and lock the screed 20 in the transport position.
Industrial Applicability
The present disclosure provides for a screed control system 100 that facilitates the cushioning of the screed 20 during travel of the paver 10. The disclosure also facilitates locking of the screed 20 in cushioned state during travel of the paver 10. The disclosure provides for enabling a smooth transition of the screed 20 from a non-cushioned state to a cushioned state.
Further, the present disclosure provides for a method 600 of cushioning a screed 20 of a paver 10. Referring to FIG. 6, the method 600 includes following steps. In step 602, the screed 20 is raised from a lowered position to a raised or transport position. The screed 20 may be raised by directing pressurized hydraulic fluid towards the rod end 34 of the actuator 30. In step 604, the actuator pressure is equalized with the accumulator pressure. The actuator pressure may be equalized with the accumulator pressure by the pressure equalization passage 340. In step 606, the screed 20 is placed in a cushioned state by connecting the actuator 30 to the accumulator 330. Once the screed 20 is raised to the raised position, the screed 20 may be placed in a cushioned state by equalizing an actuator pressure to an accumulator pressure and connecting the actuator 30 to the accumulator 330. In the embodiment illustrated, the screed 20 is placed in a cushioned state by connecting the rod end 34 of the actuator 30 to the accumulator 330. In an embodiment, the hydraulic pressure of the accumulator 330 may be equalized with the hydraulic pressure of the rod end 34 of the actuator 30 before the screed 20 is placed in a cushioned state. In an embodiment, a pressure equalization passage 340 may be provided to connect the actuator's rod end 34 with the accumulator 330 to equalize the pressure between the two. Equalizing of the hydraulic pressure of the accumulator 330 with the current hydraulic pressure of the rod end 34 of the actuator 30 enables a smooth transition of the screed 20 from a non-cushioned state to a cushioned state.
The disclosed method 600 may further include determining whether the screed 20 is in the raised position. The position detection device 40 may detect the position of the screed 20. Based on the feedback from the position detection device 40, the controller 500 may determine position of the screed 20. When the screed 20 is in the raised position, the stop member 52 may be extended to restrict or lock the screed 20 in the raised position. The controller 500 may determine the raised or lowered position of the screed 20 based on signal from the position detection device 40.
In alternate embodiments, once the screed 20 is placed in the cushioned state, travel of the screed 20 out of the transport or raised position may be restricted by extending a stop member 52. The stop member 52 restricts or locks the downward travel of the screed 20 when the screed 20 is in a transport position and/or a cushioned state. In an embodiment, the method 600 may further include providing a damping orifice 410 between the rod end 34 of the actuator 30 and the accumulator 330. The damping orifice 410 restricts free flow of the hydraulic fluid in the rod end conduit 104 and thus damps any downward movement of the screed 20.
In an embodiment, the method 600 may further include determining an operator request to move the screed 20 to a lowered position. On receiving a request to lower the screed 20, the stop member 52 may be retracted and the screed 20 may be moved to the lowered position.
Using the method and system according to the present disclosure, the screed 20 may be switched to a cushioned state smoothly, as the pressure of the accumulator 330 is equalized with the pressure of the rod end 34 of the actuators 30 before switching the screed 20 into the cushioned state. This way, when the accumulator 330 is connected to the rod end 34 of the actuator 30 for cushioning the screed 20, absence of any pressure difference between the rod end 34 and the accumulator 330 leads to smooth transitioning of the screed 20 into the cushioned state.
Also, the present disclosure provides for switching the screed 20 to the cushioned state once the screed 20 is raised to a transport position. The screed control system 100 may include a controller 500 that is coupled to the control module 200, cushioning system 300, damping system 400 and locking system 50, and a position detection device 40. The position detection device 40 may determine when the screed 20 is in a raised position, a transport position or above a certain predetermined height and send a signal to the controller 500. The controller 500 may, on receiving the signal that the screed 20 is in a transport position, control various valves in the screed control system 100 to switch the screed 20 to the cushioned state by connecting the rod end 34 of the actuator 30 to the accumulator 330, allowing the screed 20 to be automatically switched to a cushioned state once the screed 20 is detected in a transport position.
In an alternate embodiment, the controller 500 may be configured to receive instructions from the operator to put the screed 20 into a transport state. Upon receiving such instructions, the controller 500 may be configured to raise the screed 20 to a transport position and then engage the cushioned state. For raising the screed 20, the controller 500 may signal the control module 200 to send pressurized hydraulic fluid towards the rod end 34 of the actuator 30. Once the screed 20 is raised to a transport position, the controller 500 may signal the cushioning system 300 to switch the screed 20 to a cushioned state by actuating the accumulator valve 320 and cut-off valve 310 to connect the rod end 34 of the actuator 30 to the accumulator 330.
Further, the screed control system 100 according to the present disclosure provides for locking of the screed 20 in the transport position when the screed 20 is switched into a cushioned state. In an embodiment, the position detection device 40 may send signal to the controller 500 once the screed 20 is raised to a transport position. On receiving such signal, the controller 500 may be configured to switch the screed 20 to a cushioned state and extend the stop member 52 to a locking position in order to lock the screed 20 in the transport position. This way the screed 20 may be automatically locked into the transport position once the screed 20 is raised to a transport position and switched to a cushioned state. Thus the present disclosure provides for an easy operation of the screed 20 of a paver 10. In an embodiment, switching the screed 20 to a transport state may include engaging the locking system 50 once the screed 20 is switched to a cushioned state.

Claims

What is claimed is:

1. A paver comprising:

a screed;

an actuator coupled to the screed and configured to raise the screed to a transport position by pressurizing a raise end of the actuator;

an accumulator selectively connected to the actuator;

a control valve configured to switch the screed in the transport position between a non-cushioned state and a cushioned state by connecting the accumulator to the raise end in the cushioned state;

wherein an accumulator hydraulic pressure is equalized to an actuator hydraulic pressure before the control valve switches the screed from the non-cushioned state to the cushioned state.

2. The paver of claim 1, further comprising a pressure equalization passage connecting the actuator and the accumulator for equalizing the accumulator hydraulic pressure with the actuator hydraulic pressure.

3. The paver of claim 1, further comprising a damping orifice between the raise end and the accumulator.

4. The paver of claim 1, further comprising a one way check valve between the raise end and the accumulator.

5. The paver of claim 1, further comprising a controller operatively coupled to the actuator and the control valve, and wherein the controller configured to switch the screed to the cushioned state when the screed is in the transport position.

6. The paver of claim 5, further comprising a stop member, and wherein the controller is configured to move the stop member to restrict travel of the screed out of the transport position when the screed is in the cushioned state.

7. The paver of claim 1, wherein the actuator includes a first actuator connected to a first end of the screed and a second actuator connected to a second end of the screed.

8. The paver of claim 7, wherein the control valve is configured to connect the accumulator to the raise end of the first actuator and to the raise end of the second actuator in the cushioned state.

9. A paver comprising:

a screed;

an actuator coupled to the screed and configured to move the screed between a raised position and a lowered position;

a control valve configured to switch the screed between a non-cushioned state and a cushioned state in the raised position; and

a controller operatively coupled to the actuator and the control valve, the controller configured to raise the screed to the raised position and switch the screed to the cushioned state when the screed is in the raised position.

10. The paver of claim 9, further comprising an accumulator, wherein an accumulator hydraulic pressure is equalized to an actuator hydraulic pressure before the screed is switched to the cushioned state.

11. The paver of claim 10, further comprising a pressure equalization passage connecting the actuator and the accumulator.

12. The paver of claim 9, further comprising a stop member configured to block movement of the screed out of the raised position.

13. The paver of claim 10, further comprising a damping orifice between a raise end of the actuator and the accumulator.

14. The paver of claim 12, wherein the controller is configured to control movement of the stop member based on an operator input.

15. A method of cushioning a screed comprising:

raising the screed from a lowered position to a raised position;

equalizing an actuator pressure to an accumulator pressure; and

placing the screed in a cushioned state by connecting the actuator to the accumulator.

16. The method of claim 15, further comprising determining whether the screed is in the raised position.

17. The method of claim 16, further comprising extending a stop member to lock the screed in the raised position when the screed is in the raised position.

18. The method of claim 17, further comprising determining an operator request to move the screed to the lowered position.

19. The method of claim 18, further comprising retracting the stop member after receiving the operator request to move the screed to the lowered position.

20. The method of claim 19, further comprising moving the screed from the raised position to the lowered position.