Road milling machine and method for measuring the milling depth

Abstract

A method for measuring the milling depth of a road milling machine, the machine being operative to mill a ground surface with a milling roller lowered to a milling depth to create a milling track, the machine including at least one side plate located to at least one side of the milling roller to engage an untreated ground surface, and the machine including a stripping plate operative to be lowered onto the milling track generated by the milling roller. The method includes measuring the milling depth of the milling track, the measuring including detecting a measurement value of a ground engaging sensor engaging the milling track.

Claims

1. A method for measuring the milling depth of a road milling machine, the machine being operative to mill a ground surface with a milling roller lowered to a milling depth to create a milling track, the machine including a machine frame supported from a plurality of ground engaging units by a plurality of lifting columns, the milling roller being attached to the machine frame, the machine including at least one side plate located to at least one side of the milling roller to engage an untreated ground surface, and the machine including a stripping plate operative to be lowered onto the milling track generated by the milling roller, the method comprising: (a) measuring the milling depth of the milling track, the measuring including detecting a measurement value relative to the machine frame of at least one ground engaging sensor; (b) adjusting the milling depth of the milling track by adjusting an extension of at least a first one of the lifting columns to adjust a height of the machine frame; and (c) automatically controlling a lifted condition of at least a second one of the lifting columns to establish a predetermined inclination front to rear of the machine frame.

2. The method of claim 1, wherein: in step (b) the at least a first one of the lifting columns includes at least one front lifting column; and in step (c) the at least a second one of the lifting columns includes at least one rear lifting column.

3. The method of claim 1, wherein: in step (b) the at least a first one of the lifting columns includes two front lifting columns; and in step (c) the at least a second one of the lifting columns includes two rear lifting columns.

4. The method of claim 1, wherein: in step (b) the at least a first one of the lifting columns includes two front lifting columns.

5. The method of claim 1, wherein: in step (c) the at least a second one of the lifting columns includes two rear lifting columns.

6. The method of claim 1, wherein: in step (a) the at least one ground engaging sensor includes the at least one side plate.

7. The method of claim 1, wherein: in step (c) the predetermined longitudinal inclination comprises the machine frame being parallel to the ground surface.

8. The method of claim 1, wherein: in step (c) the predetermined longitudinal inclination comprises the machine frame being parallel to the milling track.

9. The method of claim 1, wherein: in step (c) the predetermined longitudinal inclination comprises the machine frame being parallel to a predetermined desired milling plane.

10. The method of claim 1, wherein: in step (c) the predetermined longitudinal inclination comprises the machine frame being parallel to a horizontal plane.

11. The method of claim 1, wherein: step (c) further comprises establishing parallelism between the machine frame and the ground surface at a desired milling depth.

12. The method of claim 1, further comprising: determining a milling depth correction in the event the machine frame is not parallel to the ground surface.

13. The method of claim 1, wherein: step (c) further comprises automatically controlling the lifted condition of at least the second one of the lifting columns with a controller.

14. The method of claim 13, wherein: in step (b) the controller automatically adjusts the milling depth at least in part in response to the measurement value detected by the at least one ground engaging senor in step (a).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a cold milling machine.

(2) FIG. 2 illustrates a first sensor means attached to the stripping plate.

(3) FIG. 3 shows two piston/cylinder units for lifting or lowering the stripping plate of a stripping means.

(4) FIG. 4 illustrates an optical device for measuring the positional difference between the side plates and the stripping means.

(5) FIG. 5 shows a cable line measuring means provided between the side plates and the stripping means.

(6) FIG. 6 illustrates a preferred embodiment.

(7) FIGS. 7a, b, c are schematic illustrations of the measurement error occurring at the stripping plate of the stripping means in the absence of parallelism between the machine frame and the ground or traffic surface. FIG. 7a is a schematic illustration showing the forward end of the machine frame tilted downward relative to the ground surface. FIG. 7b is a schematic illustration similar to FIG. 7a showing the forward end of the machine frame tilted upward relative to the ground surface. FIG. 7c is a schematic illustration similar to FIG. 7a showing the machine frame parallel to the ground surface.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) The road milling machine illustrated in FIG. 1 comprises a machine frame 4 supported by a track assembly having two front chain tracks 2 and at least one rear chain track 3. The chain tracks 2, 3 are connected with the machine frame 4 via lifting columns 12, 13. It is understood that wheels may be used instead of the chain tracks 2, 3.

(9) Using the lifting columns 12, 13, the machine frame 4 can be lifted or lowered or moved to take a predetermined inclined position with respect to the ground or traffic surface 8. The milling roll 6 supported in the machine frame 4 is enclosed by a roll case 9 which is open at the front, seen in the travelling direction, towards a conveyor belt 11 that conveys the milled material in a front part of the machine frame 4 to a second conveyor means 13. The second conveyor means 13 with which the milled material may be delivered onto a truck, for example, is not fully illustrated in FIG. 1 because of its length. Behind the milling roll 6, a height-adjustable stripping means 14 is arranged which, in operation, has a stripping plate 15 engage into the milling track 17 formed by the milling roll 6 and strip the bottom of the milling track 17 so that no milled material is left in the milling track 17 behind the stripping plate.

(10) Above the milling roll 6, a driver's stand 5 with a control panel for the vehicle operator is provided for all control functions of the driving and milling operations. It also includes a control means 23 for controlling the milling depth of the milling roll 6.

(11) The side plates 10, arranged on either side near the front end of the milling roll 6, and the stripping means 14 are provided with measuring means 16 that allow the determination of the current milling depth at the level of the stripping means 14 or the calculation of the milling depth at the level of the rotational axis of the milling roll. Here, the milling depth is determined in a plane orthogonal to the ground or traffic surface, which plane is parallel to the rotational axis of the milling roll and includes the rotational axis.

(12) The position of a first sensor means, e.g. the side plates 10, on the ground or traffic surface 8 and/or the lowering of a second sensor means, e.g. the stripping means, can thus be detected. Measuring means 16, preferably formed by position sensing means, measure the displacements of the sensor means, e.g. the side plates 10 or a beam 20 or the stripping plate 15, with respect to the machine frame 4 or relative to each other.

(13) The embodiment illustrated in FIG. 2 shows a beam 20 as the sensor means, resting on the ground or traffic surface 8 and guided at the stripping plate 15 of the stripping means in a slot 24 extending linearly and orthogonally to the bottom edge 19 of the stripping plate 15. It is understood that two mutually parallel slots 24 can be provided in the stripping plate 15 or that the beam 20, serving as the sensing means, can be guided in a different manner so as to be height-adjustable at the stripping means 14. The measuring means 16, provided in the form of a position sensing means, detects the displacement of the beam 20 with respect to the stripping means 14. Should two horizontally spaced slots 24 be used, it is possible to separately detect the milling depth on the left side of the milling track 17 and on the right side of the milling track 17. Moreover, this offers the possibility to determine an inclination of the machine frame 4 with respect to the ground or traffic surface 8.

(14) FIG. 3 illustrates another embodiment wherein the stripping plate 15 of the stripping means 14 can be lifted or lowered by means of hydraulic means. The hydraulic means are formed by piston/cylinder units 26, 28 with an integrated position sensing system. This means that the piston/cylinder units 26, 28 not only allow for the stroke movement of the stripping means, but moreover generate a position signal.

(15) As is evident from FIG. 3, the piston/cylinder units 26, 28 have one end connected to the machine frame 4 and the other end connected to the stripping plate 15.

(16) FIG. 4 illustrates an embodiment, wherein the relative movement between the side plates 10 and the stripping plate 15 is measured directly in order to detect the milling depth of the milling track 17. To achieve this, elements 38, 40 of the measuring means 16 are provided, e.g., at the side plates 10 and opposite thereto at the stripping plate 15, which elements allow for the detection of the relative displacement of the stripping plate 15 with respect to the side plates 10. This displacement corresponds to the milling depth s in FIG. 4. For example, such a measuring means, which measures relative displacements, may be formed by an optical system, e.g. by reading a scale with an optical sensor, or by an electromagnetic or inductive system.

(17) As an alternative and as illustrated in FIG. 5, the relative position sensing system between the side plates 10 and the stripping plate 15 may also be formed by a cable line 22 in combination with a cable-line sensor 21. the cable line 22 is coupled with the stripping plate 15 of the stripping means 14 on the one hand and, on the other hand, with at least one of the side plates 10 via a guide roller 35, so that the signal from the cable-line sensor 21 can immediately indicate the value of the current milling depth.

(18) The side plates 10 themselves can be used as first sensor means by monitoring their position with respect to the machine frame 4 or the second sensor means by means of a cable line and a cable-line sensor or by means of piston/cylinder units 30, 32 with integrated position sensing means.

(19) For example, the measuring means can also measure the displacement of the side plates 10 with respect to the machine frame 4. Should two measuring means be used, one in front of the side plates 10 and one behind the same, seen in the travelling direction, it is also possible to determine the longitudinal inclination of the machine frame 4 with respect to the ground or traffic surface 8 or to also determine the transverse inclination of the machine frame 4 by a comparison of the measured values for both side plates 10 on both sides of the milling roll 6.

(20) FIG. 6 illustrates a preferred embodiment, wherein cable lines 22 comprising cable-line sensors 21 mounted to the machine frame 4 are arranged on both sides of the stripping means 15. On either side of the machine, the side plates 10 are also provided with cable lines 22 and cable-line sensors 21 fastened at the machine frame 4. The milling depth s is determined from the difference between the measured values of the cable-line sensors 21 for the side plates 10 and the cable-line sensors 21 of the stripping means 15. Here, the measurement should preferably be made in the same substantially vertical plane in order to avoid measurement errors.

(21) FIGS. 7a to 7c illustrate the cable-line sensors 21 for the side plates 10 and the stripping plates 14, the drawings only indicating one cable-line sensor 21, since the cable-line sensors are arranged one behind the other in substantially the same plane.

(22) FIGS. 7a, b, c are to illustrate the case where the ground or traffic surface 8 is not parallel to the machine frame 4, the measured milling depth value indicated by the measuring means having to be corrected because of an angle error, because a longitudinal inclination of the machine frame 4 corrupts the measurement signal at the level of the stripping plate 15 or a second sensor means near the stripping means 14. Due to the fixed geometrical relations, i.e. the distance of the stripping plate 15 from the rotational axis of the milling roll 6, the measured milling depth value can be corrected, knowing the angular deviation from the horizontal in the travelling direction, and the current milling depth at the level of the milling roll axis can be calculated. The angular deviation in the travelling direction may be determined, for example, from the position of the lifting columns 12, 13 of the caterpillar track assemblies 2, 3 or the piston/cylinder units 30, 32.

(23) It is further evident from FIGS. 7a to c, to which extent the side plates 10 are pivotable with respect to the machine frame 4. Since the piston/cylinder units 30, 32 are also provided with position sensing systems, these measuring signals may be used as an alternative to cable-line sensors 21 to determine the distance of the side plates 10 from the machine frame 4.

(24) FIG. 7c illustrates the position of the at least one side plate 10 for a ground-parallel position of the machine frame 4. The stripping plate 15 illustrated in FIGS. 7a to 7c is located at the roll case 9, so that the distance of the stripping plate 14 from the rotational axis to the milling roll 6 can be determined unambiguously in order to allow for a calculation of the milling depth correction should the machine frame 4 not be parallel to the ground.

(25) The control means 23 can calculate the current milling depth at the level of the milling roll axis from the position sensing signals received, and it can possibly also generate a control signal for a vertical adjustment of the milling roll 6.

(26) Preferably, the control means 23 can automatically control the lifted condition of the at least one rear lifting column 13, seen in the travelling direction, to establish parallelism between the machine frame 4 and the ground or traffic surface 8 or to the horizontal plane or to a predetermined desired milling plane.

(27) Although the invention has been described and illustrated with reference to specific embodiments thereof, it is not intended that the invention be limited to those illustrative embodiments. Those skilled in that art will recognize that variations and modifications can be made without departing from the true scope of the invention as defined by the claims that follow. It is therefore intended to include within the invention all such variations and modifications as fall within the scope of the appended claims and equivalents thereof.