Road construction machine, crawler track unit of a road construction machine, as well as method for tensioning a chain of a crawler track unit

Patent metadata

Field	Value
Publication number	US-10562573-B2
Application number	US-201514691705-A
Country	US
Kind code	B2
Filing date	Apr 21, 2015
Priority date	Mar 20, 2009
Publication date	Feb 18, 2020
Grant date	Feb 18, 2020

Abstract

A road construction machine includes a machine frame and two front and two rear crawler track units. Each crawler track unit includes a piston-cylinder unit. A central pressure limiting valve communicates a hydraulic pressure source with a hydraulic supply line. The hydraulic supply line communicates the central pressure limiting valve with the piston-cylinder units of all four crawler tracks. A common pressure accumulator is communicated with all four of the piston-cylinder units.

First claim

The invention claimed is:

1. A road construction machine, comprising:
a machine frame;
two front crawler track units and two rear crawler track units supporting the machine frame, each crawler track unit including:
a guide wheel having a guide wheel axis;
a drive wheel having a drive wheel axis;
a continuous chain extending around the guide wheel and the drive wheel;
at least one track roller which rolls on the chain; and
an adjustment device including a piston-cylinder unit, the piston-cylinder unit including a piston to which a hydraulic adjusting pressure can be applied to generate a piston force acting on at least one of the guide wheel and the drive wheel to adjust an axis spacing between the guide wheel axis and the drive wheel axis;

a hydraulic pressure source;
a central pressure limiting valve communicated with the hydraulic pressure source;
a hydraulic supply line communicating the central pressure limiting valve with the piston-cylinder units of all four of the crawler track units so that an equal hydraulic adjusting pressure is applied to all four of the piston-cylinder units; and
a common pressure accumulator separate from the hydraulic pressure source, the pressure accumulator being communicated with all four of the piston-cylinder units.

2. The road construction machine of claim 1 , wherein:
the pressure accumulator is communicated with the hydraulic supply line, so that the pressure accumulator is subjected to the same hydraulic adjusting pressure as the piston-cylinder units.

3. The road construction machine of claim 1 , further comprising:
a sensor operatively associated with the piston of at least one of the piston-cylinder units to detect when the piston comes to a standstill relative to the cylinder after application of hydraulic adjusting pressure to the piston; and
a controller operatively associated with the sensor, the controller operable to maintain pressure communication between the central pressure limiting valve and the piston-cylinder units until detection that the piston of the at least one of the piston-cylinder units is at standstill.

4. The road construction machine of claim 3 , wherein:
the sensor includes a pressure sensor configured to detect a pressure or a change in pressure in the at least one of the piston-cylinder units.

5. The road construction machine of claim 3 , wherein:
the sensor includes a force sensor configured to detect a piston force acting on the at least one of the guide wheel and the drive wheel of the at least one of the piston-cylinder units.

6. The road construction machine of claim 3 , wherein:
the sensor includes a displacement sensor configured to detect a position of the piston of the at least one of the piston-cylinder units.

7. The road construction machine of claim 1 , further comprising:
a controller operable to maintain pressure communication between the central pressure limiting valve and the piston-cylinder units until a predetermined lapse of time after initial application of hydraulic adjusting pressure to the pistons of the piston-cylinder units.

8. The road construction machine of claim 1 , further comprising:
a controller operable to maintain pressure communication between the central pressure limiting valve and the piston-cylinder units until a counterforce between the axles of the drive wheel and guide wheel equals the piston force acting on the drive wheel and guide wheel of at least one of the piston-cylinder units.

9. The road construction machine of claim 1 , further comprising:
a distance sensor operatively associated with the chain of at least one of the crawler track units for detecting slack in an upper strand of the chain; and
a controller operatively associated with the sensor, the controller operable to maintain pressure communication between the central pressure limiting valve and the piston-cylinder units until after detection of a predetermined slack in the upper strand of the chain.

10. A method of operating a road construction machine including two front crawler track units and two rear crawler track units supporting a machine frame, each crawler track unit including:
a guide wheel having a guide wheel axis;
a drive wheel having a drive wheel axis;
a continuous chain extending around the guide wheel and the drive wheel;
at least one track roller which rolls on the chain; and
an adjustment device including a piston-cylinder unit, the piston-cylinder unit including a piston to which a hydraulic adjusting pressure can be applied to generate a piston force acting on at least one of the guide wheel and the drive wheel to adjust an axis spacing between the guide wheel axis and the drive wheel axis;

wherein the method comprises:
(a) simultaneously applying a hydraulic adjusting pressure from a common hydraulic pressure source with a central pressure limiting valve to all four of the piston-cylinder units to adjust an axis spacing between the guide wheel axis and the drive wheel axis of each of the crawler track units; and
(b) isolating the piston-cylinder units from the common hydraulic pressure source prior to engaging the crawler track units to drive the road construction machine.

11. The method of claim 10 , wherein:
in step (a) the hydraulic adjusting pressure is applied to the four piston-cylinder units until a piston of at least one of the piston-cylinder units comes to a standstill.

12. The method of claim 10 , wherein:
in step (a) the hydraulic adjusting pressure is applied to the four piston-cylinder units until a predetermined lapse of time after initial application of hydraulic adjusting pressure to the piston-cylinder units.

13. The method of claim 10 , wherein:
step (a) further comprises detecting a slack in an upper strand of the chain of at least one of the crawler-track units, and wherein the hydraulic adjusting pressure is applied to the four piston-cylinder units until after detection of a predetermined slack in the upper strand of the chain.

14. The method of claim 10 , further comprising:
communicating all four of the piston-cylinder units with a common pressure accumulator.

15. The method of claim 14 , wherein:
the communicating step further comprises communicating the pressure accumulator with a supply line communicating the common hydraulic pressure source with the four piston-cylinder units.

16. The method of claim 10 , wherein:
step (a) is automatically performed during a break in operation of the construction machine.

17. The method of claim 10 , wherein:
step (a) is automatically performed at each initial start in operation of the construction machine.

18. The method of claim 10 , wherein:
step (a) is automatically performed after a time interval.

19. The method of claim 10 , further comprising:
maintaining the four piston-cylinder units in communication with each other during operation of the construction machine so that a pressure peak in one piston-cylinder unit can be compensated, at least partially, by the other three piston-cylinder units.

Assignees

• Wirtgen Gmbh

Inventors

• Busley Peter
• Frank Burkhard
• Barimani Cyrus

Classifications

• B62D55/30

  Track-tensioning means · CPC title

• B62D55/305

  acting on pivotably mounted idlers · CPC title

• B62D55/065 Primary

  Multi-track vehicles, i.e. more than two tracks {(soil-shifting machines E02F; mining machines E21C)} · CPC title

• B62D55/0655

  Articulated endless track vehicles (steering specially adapted for trailers B62D13/00; articulated buses B62D47/025; tractor-trailer combinations or road trains comprising a uni-axle unit and a uni-axle trailer B62D53/02) · CPC title