GB1569648A

GB1569648A - Screed board for concrete road finishers

Info

Publication number: GB1569648A
Application number: GB1752078A
Authority: GB
Original assignee: Joseph Voegele AG
Current assignee: Joseph Voegele AG
Priority date: 1977-05-03
Filing date: 1978-05-03
Publication date: 1980-06-18
Also published as: FR2389716A1; DE2719692A1

Description

(54) SCREED BOARD FOR CONCRETE ROAD FINISHERS (71) We, JOSEPH VÖGELLE A.G., of Neckarauer Strasse 168-228, 6800 Mannheim 1, West Germany, a German company, do hereby declare this invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a screed board for concrete road finishers, comprising a main screed board, which is preferably divided for enabling a road profile to be set which slopes from the middle towards the sides of the road, and at least one additional screed board which extends approximately half the length of the main screed board and lies after the main screed board as considered in the direction in which the concrete is placed, the additional screed board being outwardly movable, relative to the main screed board, for enabling the width of the concrete being placed to be increased, both the main screed board and the additional screed board being equipped with at least one vibration device.

The compacting by vibration, over a large surface area, of bulk material (e.g. road surfacing material, which has been spread out) necessitates, if this compacting is to be uniform and optimal in its efficiency, a strict observance of the principle that all individual masses, to which vibration can be imparted, of a multi-part surface compacting system must vibrate with perfect synchronism. If this synchronism cannot be realised, it is questionable whether the desired effect will be attained. Resonance phenomena, which occur if the required synchronism is not present, not only make it impossible to control the compacting effect but may actually cause the concrete to be totally or partially loosened rather than compacted.

This subdivision of the compacting surfaces of so-called expansible screed boards, which usually consist of a main screed board (which is divided for setting a road profile which slopes from the middle towards the sides of the road) and at least one displaceable additional screed board, necessitates the use of - multi-part vibration devices, so that, in the case of these so-called expansible screed boards, synchronism of the vibrations is of particular importance.

The mechanical vibration devices hitherto used with screed boardsthese mechanicalvibration devices being constituted as unbalanced vibrators--enable, in the case of a continuous main screed board, synchronism of the vibration effects to be achieved, and a desired frequency to be set.

The transmission of the vibration drive from the main screed board to the additional screed board is, due to the fact that the additional screed board is displaceable, associated with considerable expense, although it still does not ensure with absolute certainty synchronism of the vibrations.

Electromagnetic vibration devices ensure synchronism of vibration, but are very sensitive to alterations in the weight ratios, or conditions of the masses concerned, which are the result of fluctuations in the concrete placing behaviour and in the amenability to compacting of the highway surfacing material. In the case of an electromagnetic vibration device, alteration in the weight of the materials present leads to a so-called "stop operation" and, hence, to mechanical disturbances. In the case of electromagnetic vibration devices, alteration in the frequency is only possible if elaborate and expensive electrical means are provided for this purpose.

Accordingly, an object underlying the invention is that of so constructing a screed board for concrete road finishers-this screed board comprising a main screed board and at least one movable additional screed board-that all parts of the screed board can, without large expense being entailed, vibrate synchronously, alterations both in amplitude and in frequency being possible.

According to the invention this object is realised, in the case of a screed board asset forth above, by arranging for the vibration devices to consist of hydraulic pulsation devices, which are known per se and are connected to a common hydraulic pulse generator of known construction. By means of the pulse generator all pulsators vibrate synchronously. The speed of the pulse generator is adjustable, so that the frequency of the vibrations of the pulsators can be altered. Through the quality of oil, which is uniformly fed to the pulsators by the pulse generator, the amplitude of the pulsators and, hence, the amplitude of the screed boards, can be altered. The strength of the oil pulses is affected by altering the pressure of the pulsating oil current.These three factors enable, in all driving conditions and all road surfacing conditions, the pulsators to be adjusted so as to achieve optimal compacting work.

The invention is explained below in greater detail with reference to an embodiment illustrated in the drawing, in which: Figure 1 is an oblique view of a screed board according to the invention, and Figure 2 schematically illustrates the way in which the pulsators are connected to the pulse generator.

In Figure 1 of the drawing 1 designates a screed board, which, by way of partially shown support arms 2, is articulated to a concrete road finisher (not shown) so as to be adjustable, in height and inclination, relative to the concrete road finisher. The screed board 1 has a main board 3, which is rigidly connected to the supporting arms 2, and is divided in the centre so as to enable a road profile to be set which slopes from the middle towards the sides of the road.

Behind this main screed board 3 are two additional screed boards 4, 5, which extend approximately half the length of the main board 3 and can be moved towards the outside, relative to the main board 3, so as to enable the width of the area over which concrete is to be placed to be increased. In a known manner (not illustrated) the two additional screed boards 4, 5 are guided both on the main board 3 and also on the supporting arms 2 and, by way of an hydraulically actuatable piston and cylinder unit 6, 7, can be moved laterally towards the outside, and back, from their starting or basic position.

On each part of the main screed board 3 and on each of the additional boards 4, 5, there is arranged a respective hydraulic pulsator 8, which is constituted as a double acting piston and cylinder unit, having a short working stroke. The pulsators 8 are arranged in such a way that the pistons move perpendicularly of the main surface of the main screed board 3 and of the additional screed boards 4, 5. Arranged on the main board 3 is a hydraulic pulse generator 9 which communicates, by way of ducts (which are not shown in Figure 1), with all four pulsators 8. As illustrated in Figure 2, the pulse generator 9 is set in rotation by a hydraulic motor 10, which receives a flow of oil from a hydraulic pump 11, which is for example driven by an electric motor.

The speed of the hydraulic motor 10 can be controlled by means of the hydraulic pump 11. In the embodiment illustrated, the flow of oil arriving from the hydraulic motor 10 is fed to the pulse generator 9. The pulse 'generator 9 is so constructed that, in the course of its rotary movement, it converts this oil flow, continuously fed to it, into two pulsating oil streams, and passes these pulsating oil streams to the two sides of the pulsators 8. Consequently, the pulsators 8 execute vibrations in the frequency of the arriving pulses, the amplitude of which vibrations depends on the quantity of oil, the oil pressure, and the effective piston surface. The oil pressure can be adjusted by a pressure limiting valve 15 as a result of which the amplitude can be controlled.

By means of a volume governor 13 the frequency of the vibrations is determined by altering the speed of the hydraulic motor 10.

WHAT WE CLAIM IS:- 1. A screed board for concrete road finishers, comprising a main screed board and at least one additional screed board which extends approximately half the length of the main screed board and which lies, in the direction of concrete placement, after the main screed board, this additional screed board being outwardly movable, relative to the main screed board, so as to enable the width of the concrete being placed to be increased, both the main screed board and also the additional board being equipped with at least one vibrator device, wherein the vibrator devices are each in the form of a hydraulic pulsation unit, which units are connected to a common hydraulic pulse generator.

2. A screed board according to claim 1, wherein the pulsation units are formed as piston and cylinder units.

3. A screed board according to claim 1, wherein the pulsation units are constituted by a housing with a diaphragm.

4. A screed board according to claim 1, 2 or 3, wherein the main screed board is divided for setting a road profile which slopes from the middle towards the sides of the road.

5. A screed board according to any one of the preceding claims, comprising two

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. According to the invention this object is realised, in the case of a screed board asset forth above, by arranging for the vibration devices to consist of hydraulic pulsation devices, which are known per se and are connected to a common hydraulic pulse generator of known construction. By means of the pulse generator all pulsators vibrate synchronously. The speed of the pulse generator is adjustable, so that the frequency of the vibrations of the pulsators can be altered. Through the quality of oil, which is uniformly fed to the pulsators by the pulse generator, the amplitude of the pulsators and, hence, the amplitude of the screed boards, can be altered. The strength of the oil pulses is affected by altering the pressure of the pulsating oil current.These three factors enable, in all driving conditions and all road surfacing conditions, the pulsators to be adjusted so as to achieve optimal compacting work. The invention is explained below in greater detail with reference to an embodiment illustrated in the drawing, in which: Figure 1 is an oblique view of a screed board according to the invention, and Figure 2 schematically illustrates the way in which the pulsators are connected to the pulse generator. In Figure 1 of the drawing 1 designates a screed board, which, by way of partially shown support arms 2, is articulated to a concrete road finisher (not shown) so as to be adjustable, in height and inclination, relative to the concrete road finisher. The screed board 1 has a main board 3, which is rigidly connected to the supporting arms 2, and is divided in the centre so as to enable a road profile to be set which slopes from the middle towards the sides of the road. Behind this main screed board 3 are two additional screed boards 4, 5, which extend approximately half the length of the main board 3 and can be moved towards the outside, relative to the main board 3, so as to enable the width of the area over which concrete is to be placed to be increased. In a known manner (not illustrated) the two additional screed boards 4, 5 are guided both on the main board 3 and also on the supporting arms 2 and, by way of an hydraulically actuatable piston and cylinder unit 6, 7, can be moved laterally towards the outside, and back, from their starting or basic position. On each part of the main screed board 3 and on each of the additional boards 4, 5, there is arranged a respective hydraulic pulsator 8, which is constituted as a double acting piston and cylinder unit, having a short working stroke. The pulsators 8 are arranged in such a way that the pistons move perpendicularly of the main surface of the main screed board 3 and of the additional screed boards 4, 5. Arranged on the main board 3 is a hydraulic pulse generator 9 which communicates, by way of ducts (which are not shown in Figure 1), with all four pulsators 8. As illustrated in Figure 2, the pulse generator 9 is set in rotation by a hydraulic motor 10, which receives a flow of oil from a hydraulic pump 11, which is for example driven by an electric motor. The speed of the hydraulic motor 10 can be controlled by means of the hydraulic pump 11. In the embodiment illustrated, the flow of oil arriving from the hydraulic motor 10 is fed to the pulse generator 9. The pulse 'generator 9 is so constructed that, in the course of its rotary movement, it converts this oil flow, continuously fed to it, into two pulsating oil streams, and passes these pulsating oil streams to the two sides of the pulsators 8. Consequently, the pulsators 8 execute vibrations in the frequency of the arriving pulses, the amplitude of which vibrations depends on the quantity of oil, the oil pressure, and the effective piston surface. The oil pressure can be adjusted by a pressure limiting valve 15 as a result of which the amplitude can be controlled. By means of a volume governor 13 the frequency of the vibrations is determined by altering the speed of the hydraulic motor 10. WHAT WE CLAIM IS:-

1. A screed board for concrete road finishers, comprising a main screed board and at least one additional screed board which extends approximately half the length of the main screed board and which lies, in the direction of concrete placement, after the main screed board, this additional screed board being outwardly movable, relative to the main screed board, so as to enable the width of the concrete being placed to be increased, both the main screed board and also the additional board being equipped with at least one vibrator device, wherein the vibrator devices are each in the form of a hydraulic pulsation unit, which units are connected to a common hydraulic pulse generator.

5. A screed board according to any one of the preceding claims, comprising two

additional screed boards each outwardly movable one to each side relative to the main screed board.

6. A screed board substantially as shown in the accompanying drawing and described herein with reference thereto.

7. A concrete road finisher comprising a screed board according to any one of the preceding claims.