EP0495171B1 - Laying-down course thickness adjusting method with a finisher - Google Patents

Abstract

A method for adjusting the thickness of a course consisting of road-building material to be laid down by a finisher on a foundation by raising a laying-down board of the finisher to a height adapted to the desired thickness, and a finisher suitable therefor are described, the laying-down board of which finisher is connected to the finisher via an articulation point for floating support on the course, the articulation point being height-adjustable via a first lifting cylinder, and the laying-down board being connected to a second lifting cylinder which is unlocked during laying down. In order to simplify the adjustment of the thickness of the course to be laid down, it is proposed to place the laying-down board flat on the foundation for initial adjustment of the course thickness, to determine this position by measurement transducers and subsequently to raise the laying-down board by the first and second controllably height-adjustable lifting cylinders to a height corresponding to the desired laying-down thickness plus rolling quantity. <IMAGE>

Description

The invention relates to a method for adjusting the thickness of a layer to be installed by a paver on a substrate of the type explained in the preamble of claim 1 and a suitable paver of the type explained in the preamble of claim 7.

Such a paver is known from DE-A-35 35 362. The known paver has a trailed screed that is rigidly connected to two leveling bars. The leveling bars are pivotally connected to the paver on both sides of the paver via a pivot point. With the help of a first lifting cylinder, the articulation points can be adjusted in height, so that the angle of attack of the screed, ie the angle at which the screed plate arranged under the screed runs to the ground, can be changed. This change in the angle of attack is used to vary the thickness of the layer to be installed. During operation, the screed is floating on the layer to be installed, ie it is exposed only with its own weight on the layer. In order to prevent the screed from sinking into the still soft layer due to its own weight during a stopover of the vehicle and thus causing a depression in the road surface, and to prevent the screed from starting again when starting up again of the vehicle slides onto the material that has already solidified before the intermediate stop without sufficient compression, and thus causes a start-up hump, a second lifting cylinder is provided on each of the leveling bars, which acts at a distance from the first lifting cylinder. However, this second lifting cylinder cannot be regulated, ie it cannot be moved into a predetermined position. The second lifting cylinder only serves to block the floating position of the screed, so that the screed cannot sink at an intermediate stop and is pulled over the already solid material with a rigid force when it starts again without it being able to move upwards.

In order to be able to keep a pre-selected thickness of the paving layer constant during the operation of the road paver, a measuring device is provided on the road paver, which measures the distance to a specified reference line in the area of the screed front edge and worm shaft and, in the event of deviations from the nominal value, the layer thickness by adjusting the height of the articulation point of the Leveling bars corrected.

However, the correct layer thickness must be set in a rather cumbersome manner before starting operation. For this purpose, wooden beams or the like are placed under the screed plates of the screed until the screed is at a height corresponding to the desired layer thickness plus rolling dimension. The required angle of attack can then also be set by adjusting the height of the articulation points by means of the first lifting cylinders. It is only when this setting is handled precisely that it is possible to achieve the exact paving thickness before starting construction. Nevertheless, most of the time, corrections still have to be made. Precise work is especially then This is important if you have to continue with the installation layers already laid the day before. In practice, there are almost always bumps in the road surface, which must then be laboriously removed.

DE-A-31 24 363 describes a method and a device for correcting the angle of attack of width-adjustable pavers. The known method is intended to prevent a shoulder from forming at the transition area between the main screed and the adjusting screeds if the angle of attack of the main screed also changes when the layer thickness of the paving layer changes. The screeds are articulated via leveling bars, whereby the articulation point can be adjusted in height by means of a first lifting cylinder. A second working cylinder is provided in the direction of travel behind the first lifting cylinder, which holds the screed in the floating position during operation of the paver and which can additionally be acted upon by a magnitude which can be varied to counteract the weight of the main screed. If the angle of attack changes, the load on the working cylinder changes, whereby the paver screed is raised or lowered as a result of the pressure of variable magnitude, which counteracts the weight of the main screed, until the angle of attack resumes the previously set position, with no steps between the main - and the screed occur. An encoder or button can be provided that detects such paragraphs.

DE-A-28 38 123 discloses a road paver with a device for adjusting and measuring the paving thickness and volume of road surfaces. The paver contains a screed, which is made with the help of two Working cylinders, which are the same in the direction of travel, are height-adjustable, ie the screed is not articulated via leveling bars at a pivot point. In the known device, the paving thickness and the paving volume are continuously determined during the laying of the covering and used for billing the work performed. For this purpose, marking devices are attached to the piston rods of the hydraulic cylinders, which interact with display devices, the distance between the marking device on the hydraulic cylinder and a fixed point being determined and used for billing.

AU-B-27 245/84 relates to a road paver with a box, which is attached to a pivot point via leveling bars and is open in the direction of travel for receiving the paving material. The pivot point can be adjusted in height using a lifting cylinder. A transducer is provided which scans unevenness in the surface. A second transducer is used to measure the thickness of the finished layer. How the layer thickness is initially set is not described.

The invention has for its object to provide a method and a paver for performing the method with which an exact adjustment of the thickness of a paving layer is possible.

The object is achieved in a method by the characterizing features of claim 1.

The invention proposes the lifting cylinders in conjunction with in order to initially adjust the thickness of the installation layer to use two transducers spaced apart in the direction of travel, the height of the second lifting cylinder also having to be designed. By laying the screed flat on the subsoil, a reference value can be obtained in a simple manner, to which only the desired paving thickness plus rolling dimension then has to be added or subtracted, depending on the measuring method.

The measure according to claim 2 allows the paving thickness of the road building material to be corrected during the installation, without the need for manual measurements.

According to claim 3, the reference value for the position of the screed is determined by a simple distance measurement, where as the fixed point for the distance measurement according to claims 4 to 6 either the subsurface itself, or a fixed point arranged on the paver or any other fixed point lying outside the screed and the paver is used, the latter solution having the advantage that a Possibility is created to correct the paving thickness during operation in a known manner.

The task is solved in a road paver by the characterizing features of claim 7.

By arranging two height-adjustable lifting cylinders, each of which can also take over the tasks of the corresponding lifting cylinder of the known paver, the thickness of the layer can also be easily adjusted before the start of operation, with the arrangement of two transducers spaced in the direction of travel on Leveling bar of the screed the exact position of the screed can be determined as a reference value.

Due to the arrangement of the sensors on both sides, deviations in the thickness of the layer in the transverse direction to the road can be eliminated.

• Figur 1 eine Seitenansicht eines erfindungsgemäß ausgerüsteten Straßenfertigers in schematischer Darstellung, und
• Figur 2 eine schematische Darstellung des Einstellvorganges der Einbaubohle.

An embodiment of the invention is explained below with reference to the drawings. Show it:

• Figure 1 is a side view of a road paver equipped according to the invention in a schematic representation, and
• Figure 2 is a schematic representation of the setting process of the screed.

A road paver 1 can be seen in FIG. 1, which drives in the direction of arrow F on a subgrade 2 forming a subsurface. The paver 1 has a screed 3 which is provided with a smoothing plate 3a. One end of two leveling bars 4a, 4b is rigidly connected to the screed 3. The leveling bars 4a, 4b extend forward on both sides of the paver's frame and are articulated with their front free ends to the frame of the paver 1 via a respective articulation point 5a, 5b. Each of the articulation points 5a, 5b can be adjusted in height in a controlled manner in the direction of the double arrow A via a first adjustable lifting cylinder 6a, 6b. Between each of the articulation points 5a, 5b and the screed 3, a second lifting cylinder 7a, 7b, which is adjustable in the direction of the double arrow B, acts on each of the leveling bars 4a, 4b. In the vicinity of each end of each of the leveling bars 4a, 4b there is provided a sensor 8a, 8b, 9a, 9b, for example mechanical buttons or contactless sensors, such as ultrasound sensors.

In operation, the screed 3 is presented by a screw 10 road building material 11, in the present case bituminous mix, which is compacted by the screed 3 when the paver 1 is driving in the direction of arrow F to form a paving layer 12 with a predetermined thickness above the level 2 . The screed lies here 3 floating, ie with their own weight, on the mix 11 to be compacted. For this purpose, the second lifting cylinders 7a, 7b are unlocked in a known manner, so that no pressure or tensile forces are exerted on the leveling bars 4a, 4b and thereby on the screeds 3. The lifting cylinders 7a, 7b can also be used in a known manner to sink the screed 3 when the paver is stopped in the still soft paving layer 12 and slide the screed 3 after a stop to a mixture 11 that has already become firmer without sufficient compaction avoid by locking the lifting cylinders 7a, 7b in a known manner.

For the initial setting of the thickness of the paving layer 12 before the start of operation, the screed 3 is lowered so far onto the level 2 by the lifting cylinders 6a, 6b, 7a, 7b that the smoothing plate 3a of the screed 3 lies flat on the level 2. Then this position of the screed 3 is determined via the transducers 8a, 8b, 9a, 9b. In the present case, the distances of the transducers 8a, 8b, 9a, 9b, which are firmly connected to the leveling bars 4a, 4b, are determined from a fixed point. The fixed point can be either the formation 2 and / or a fixed point 13a, 13b or 14a, 14b arranged on the frame of the paver 1 and / or an exactly horizontally oriented surface lying outside the paver 1 and the formation 2, such as a curb, for example. a tensioned wire 15a, 15b or a towing ski can be used, as indicated by the arrows in FIG. 2. Then the screed 3 is raised via the first and second lifting cylinders 6a, 6b, 7a, 7b to a height above the level 2 which corresponds to the desired paving thickness, plus the rolling dimension if necessary. This position of the screed 3 is held until a floating support of the screed 3 on the road building material 11 is possible. The angle of attack of the screed 3, ie the angle of the smoothing plate 3a to the formation 2 can be adjusted or changed in a known manner by the first lifting cylinders 6a, 6b.

Due to the symmetrical arrangement of the sensors and the lifting cylinders on both leveling bars 4a, 4b, a constant paving thickness of the layer 12 is achieved across the width of the road transversely to the direction of travel F. Due to the arrangement of four sensors, the paver serves as averager over its drive length.

Over the length of the undercarriage (approx. 3m), unevenness in the formation is filtered with a short distance. This means, when using the measuring points 13a and 13b, a corresponding good averaging of the existing unevenness of the formation. Since the screed itself is a very slow mechanical structure that reacts very slowly to changes (e.g. manipulated variable on the leveling cylinder), the measured unevenness of the subgrade can also be filtered very well electrically at measuring points 9a and 9b (averaging).

The processing of the signals from the sensors, the control of the first and second lifting cylinders and the specification of the setpoints for the height of the screed are expediently carried out electronically, the position of the screed being stored on the formation as a reference value.

On a display that shows the height of the trailing edge of the smoothing plate 3a of the screed 3 to the level 2 as a second measured value from the measured values of a distance measurement, the paving thickness of the Determine road construction material and correct if necessary. However, it is necessary that the height sensor uses a ski switch to detect the reference not directly from a curb or tensioned wire, but directly from the formation.

In a modification of the described and drawn exemplary embodiment, all devices known for this purpose can be used for the sensors. With the existing sensors and control options, it can be easily ensured that the paving thickness remains constant even during normal operation. Finally, the invention can also be used in road pavers of different types.

Claims (8)

1. A method of adjusting the thickness of a layer of road building material to be laid on a base (2) by a road finisher (1), by lifting a screed (3) of the road finisher (1) relatively to a fixed point (2, 13a, 13b, 14a, 14b, 15a, 15b) to a height appropriate to the required thickness, the screed (3) being connected to the road finisher (1) via at least one point of articulation (5a, 5b) so as to rest floatingly on the said layer, the point of articulation (5a, 5b) being connected for vertical adjustment via a first lifting cylinder (6a, 6b) and the screed (3) being connected to a second lifting cylinder (7a, 7b) which is unlocked during the laying, characterised in that the screed (3) is initially lowered by both lifting cylinders (6a, 6b, 7a, 7b) until it rests flatly on the base (2), this position of the screed (3) is taken as a reference value and the screed (3) is then lifted by the two lifting cylinders (6a, 6b, 7a, 7b) to the appropriate height and is kept at that height until it is possible for the screed (3) to rest floatingly on the layer, the measurements or the reference value and the distance from the fixed point (2, 13a, 13b, 14a, 14b, 15a, 15b) being obtained from at least two locations situated consecutively in the direction of travel (F).
2. A method according to claim 1, characterised in that during the lifting of the screed (3) to the appropriate height the distance traversed by the screed (3) is measured and is used as a reference value to check the actual thickness of the required layer.
3. A method according to claim 1 or 2, characterised in that the reference value for the position of the screed (3) on the base (2) is determined by distance measurements between the screed (3) and the fixed point (2, 13a, 13b, 14a, 14b, 15a, 15b).
4. A method according to claim 3, characterised in that the base (2) is used as the fixed point.
5. A method according to claim 3, characterised in that a fixed point (13a, 13b, 14a, 14b) disposed on the road finisher (1) is used.
6. A method according to claim 3, characterised in that a fixed point (15a, 15b) situated outside the road finisher (1) and the base (2), more particularly a horizontally aligned fixed line or fixed surface, is used.
7. A road finisher (1) having a screed (3) articulated by way of levelling members (4a, 4b) and adapted to be applied floatingly, the point of articulation (5a, 5b) of the levelling member (4a, 4b) being controllably adjustable as to height by means of a first lifting cylinder (6a, 6b), a second lifting cylinder (7a, 7b) engaging the levelling member (4a, 4b) between the point of articulation (5a, 5b) and the screed (3), characterised in that measurement sensors (8a, 8b, 9a, 9b) for measuring the distance of the screed (2) from a fixed point (2, 13a, 13b, 14a, 14b, 15a, 15b) are secured directly on the levelling member (4a, 4b) and are spaced apart in the direction of travel (F), and in that the second lifting cylinder (7a, 7b) is also controllably adjustable as to height.
8. A road finisher according to claim 7, characterised in that pairs of spaced measurement sensors (8a, 9a, 8b, 9b) are provided on either side of the screed.

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