Proportional screed control for a finisher

Claim 2

A paver comprising: a tractor; a screed having a pair of spaced-apart arms pivotally connected to said tractor for towing; a pump; a pair of fluid-operated cylinders operatively connected between said tractor and respective arms of said screed; a pair of proportional servo valves connected in fluid circuit with respective fluid-operated cylinders and said pump; and proportional control means electrically connected to said servo valves for controlling the position thereof comprising a grade control device electrically connected to one of said servo valves and including means for sensing the position of the screed with respect to a desired grade reference and means for producing a grade correction signal for the associated servo valve in accordance with the sensed position, and a slope control device connected to the other of said servo valves and including means for sensing the slope of the screed with respect to a desired slope and means for producing a slope correction signal for the associated servo valve in accordance with the sensed slope of the screed.

Claim 3

The paver according to claim 1, comprising means mounting said grade control device at the screed and outboard thereof for accurate sensing of screed movement.

Claim 4

The paver according to claim 1, wherein said grade sensing means includes a movable member for continuously contacting the reference and said means for producing a grade correction signal includes a transducer coupled to said movable member.

Claim 5

The paver according to claim 1, wherein said means for proDucing a grade correction signal comprises an amplifier for amplifying the grade correction signal.

Claim 6

The paver according to claim 1, wherein said grade sensing means comprises a movable member for continuously contacting the grade reference and means mounting said grade control device at the screed and outboard thereof including adjusting means for adjusting the elevations of said grade control device.

Claim 7

A paver according to claim 1, comprising means mounting said slope control means on said screed.

Claim 8

A paver according to claim 1, wherein said slope control device includes a movable member and said means for producing a slope correction signal includes a transducer coupled to said movable member.

Claim 9

A paver according to claim 1, wherein said means for producing a slope correction signal includes an amplifier for amplifying said slope correction signal.

Claim 10

A paver according to claim 1, wherein said means for producing a slope correction signal includes an amplifier, and a reference set point unit for establishing a slope reference for said amplifier.

Claim 11

A paver according to claim 9, wherein said set point unit is a remote unit having a flexible cable connected to said slope control device.

Claim 12

A paver comprising: self-propelled means; a screed towed by said self-propelled means including a pair of spaced-apart arms movably connected to said self-propelled means; a pair of fluid-operated cylinders each connected to said self-propelled means and to respective arms adjacent the movable connections; a pump; a pair of proportional servo valves connected in respective fluid circuits with said pump and said fluid-operated cylinders and operable to permit fluid flow in response to the direction of controlling electrical signals and in proportional response to the magnitude of said electrical signals; grade control means for controlling one of said fluid-operated cylinders including grade sensing means for sensing the position of said screed with respect to a reference grade and means electrically connected to one of said servo valves for producing a grade control signal indicative of the difference and direction between the sensed position and a reference grade; and slope control means for controlling the other of said servo valves including means for sensing the slope of said screed with respect to a reference slope, and means electrically connected to the other of said servo valves for producing a slope control signal indicative of the magnitude and direction of deviation between the sensed slope and the reference slope.

Claim 13

A paver comprising: self-propelled means; a screed towed by said self-propelled means including a pair of spaced-apart arms movably connected to said self-propelled means; a pair of fluid-operated cylinders each connected to said self-propelled means and to respective arms adjacent the movable connections; a pump; a pair of proportional servo valves connected in respective fluid circuits with said pump and said fluid-operated cylinders and operable to permit fluid flow in response to the direction of controlling electrical signals and in proportional response to the magnitude of said electrical signals; grade control means for controlling one of said fluid-operated cylinders including grade sensing means for sensing the position of said screed with respect to a reference grade and means electrically connected to one of said servo valves for producing a grade control signal indicative of the difference and direction between the sensed position and a reference grade; and slope control means for controlling the other of said servo valves including means for sensing the slope of said screed with respect to a reference slope, and means electrically connected to the other of said servo valves for producing a slope control signal indicative of the magnitude and direction of deviation between the sensed slope and the reference slope.