Compaction roller

Abstract

The invention relates to a compaction roller having at least one rolling body with a vibratory drive which comprises a drivable exciter shaft with an unbalance. The shaft is mounted axially with respect to the rolling body and in the body. The unbalance, which comprises an unbalance cylinder arranged centrally with respect to the axis of the rolling body, is held by the exciter shaft and has an unbalance piston which can be adjusted hydraulically radially with respect to the axis of the rolling body by means of an adjusting device.

Description

BACKGROUND OF THE INVENTION

[0001] The invention relates to a compaction roller as it is used for the compaction of materials in earthwork and road construction.

[0002] In earthworks or road construction, it is desirable to compact unbound and hydraulic-bound or bituminous-bound materials as rapidly as possible to the prescribed Proctor or Marshall density, but at the same time to prevent over-compaction and, in particular in the case of wearing courses, to minimize particle fragmentation of the mineral constituents.

[0003] In the case of bituminous road surfaces, smoothing of the surface during compaction should be avoided in order to ensure either good bonding between courses or, in the case of wearing courses, a high level of grip. The setting of optimum system parameters for short compaction times is an absolute necessity in the case of bituminous materials since cooling of the material causes the compactability to diminish and, in the most unfavorable case, the prescribed final density cannot be achieved. When compacting drain asphalt (open-pore asphalt), the pores in the region close to the surface must not be closed, so that the desired water drainage can be obtained and the effect known as "air-pumping" reduced when automobile tires roll in the contact zone between tire and roadway.

[0004] Where vibration amplitudes of the rolling body are excessively high or where vibration frequencies are close to the natural frequency of, for example, bridge structures or other structures, it is possible that these may become damaged, so that in these cases, especially where rollers with conventional eccentrically loaded rotating shafts are concerned, the vibration has to be switched off to avoid damage. The result of this then is that, in order to reach the prescribed final density, a greater number of static roller passes is required if the final density can be achieved at all by means of static rolling.

[0005] It is known that vibratory rollers for compacting unbound soils and hydraulic or bituminous courses can be equipped with an eccentrically loaded rotating shaft. In this case, at least one fixed unbalance is provided. It is additionally possible, as is usually the case, for an additional changeover weight to be provided in order to generate two different nominal amplitudes. However, there is no possibility of adjusting the amplitude between the two nominal amplitudes.

[0006] It is also known that asphalt compaction can be performed by means of what is known as oscillation using a rolling body without circular or directional vibrations, European Patent EP 0 053 598 B. However, compaction to depth does not take place, since here the material is compacted solely by a static linear load and alternating exposure to shear stress. The enforced slip between the rolling body and ground makes traction problems unavoidable. The oscillating moment is generated by two unbalanced shafts which are mounted parallel to the axis of rotation of the roller and of which their unbalances, offset by 180.degree., run synchronously in the same direction. In the case of bituminous materials, the oscillating effect can lead to undesirable ripples, to smoothing effects and to pore closure.

[0007] In compaction rollers, it is also known for the angle between an unbalance which can be rotated around the rolling body axis, and a fixed unbalance to be adjusted so that the resulting unbalance can be set in an infinitely variable manner.

[0008] German document DE 69425111 T2 discloses a compaction roller whose unbalance, which is arranged so as to be rotatable transversely with respect to the rolling body axis, can be adjusted in an infinitely variable manner via a hydraulic cylinder and a connecting rod. However, this is very expensive and complex.

[0009] In the compaction rollers which are described in German Patent Application DE 4 129 182 A1 and European Patent Application EP 0 954 187 A2, a directional vibrator comprises at least two exciter shafts which run in opposite directions and whose resulting force can be rotated without moment in an infinitely variable manner from a horizontal direction into a vertical direction. The nominal amplitude or unbalance is not changed in this system. It is also the case here, in particular where horizontal vibrations are concerned, that undesirable ripples, smoothing effects and pore closures can occur.

[0010] German Patent Application DE 100 31 617 A1 also discloses a vibration generator for a soil compaction machine in which an exciter shaft is provided with an unbalance, a cylinder arranged radially with respect to the exciter shaft and having a spring-loaded piston being used for the purpose of bringing about automatic adjustment of the unbalance by virtue of the centrifugal force changing through a change in the speed of rotation. Apart from the fact that the high degree of non-linearity of centrifugal forces having variable eccentricity and speed of rotation cannot completely compensate for the spring forces of metal or oil springs, it is also the case here that each frequency is assigned exactly one amplitude. In addition, from a standing start the unbalance shaft can only be accelerated with a high degree of unbalance.

SUMMARY OF THE INVENTION

[0011] It is an object of the invention to provide a compaction roller which permits optimum adaptation of the vibration to the particular road building materials or to the local circumstances, such as the presence of bridges and vibration-sensitive structures and installations.

[0012] Thus, the invention concerns a compaction roller having at least one rolling body with a vibratory drive which comprises a drivable exciter shaft with an unbalance, said shaft being mounted axially with respect to the rolling body and in said body, the unbalance comprising an unbalance cylinder which is arranged centrally with respect to the axis of the rolling body, is held by the exciter shaft and has an unbalance piston which can be adjusted hydraulically radially with respect to the axis of the rolling body and to which hydraulic fluid can be supplied in a controlled manner from outside by means of an external adjusting device via a bore in the exciter shaft, with infinitely variable adaptation of the nominal amplitude to paving situations, the adjusting device having an actuating cylinder with an actuating piston and a chamber of the actuating cylinder communicating with the unbalance cylinder, wherein the chamber of the actuating cylinder in communication with the unbalance cylinder is connected via a controllable valve to a hydraulic oil source for the purpose of leakage oil replacement, which valve shuts in a central position of the unbalance piston, from which the nominal amplitude can be increased or reduced.

[0013] In this context, an actuating cylinder is provided whose chamber of the actuating cylinder in communication with the unbalance cylinder is connected via a controllable valve to a hydraulic source for the purpose of leakage oil replacement, which valve shuts in a central or intermediate position between the two end positions of the unbalance piston, from which the nominal amplitude can be increased or reduced.

[0014] This makes it possible to carry out leakage oil replacement and calibration, with the result that by so doing the compaction result is not impaired. Furthermore, it is possible in a structurally simple manner to adjust the nominal amplitude of the vibration of the rolling body. This further allows the vibration frequency and the traveling speed of the vibratory roller to be automatically adapted to the nominal amplitude, once again in order to obtain optimum compaction results. Thus, the compaction of great layer thicknesses, for example anti-frost layers, thin layer thicknesses, for example a surface layer for compact asphalt, and sensitive layers such as open-pore asphalt, can be ensured.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawings in which:

[0016] FIG. 1 shows a schematic side view of a tandem compaction roller.

[0017] FIG. 2 shows a rolling body of the tandem compaction roller of FIG. 1, in section.

[0018] FIG. 3 shows a detail of FIG. 2.

[0019] FIGS. 4a and 4b show two embodiments of an adjusting device for adjusting the nominal amplitude of the tandem compaction roller of FIG. 1.

[0020] FIGS. 5a to 5c show three different operating settings for an embodiment of the tandem compaction roller of FIG. 1.

[0021] FIGS. 6a to 6c show three different operating settings for a further embodiment of the tandem compaction roller of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] The tandem compaction roller shown in FIG. 1 comprises a superstructure 1 with driver's cab, a rolling body 2 and 3 being mounted via steerable swivel couplings 4 at the front and rear underneath said superstructure. Situated between the two rolling bodies 2, 3 is an engine compartment 5 which houses a drive engine, usually a Diesel engine.

[0023] As shown in FIG. 2, the front and/or rear rolling body 2, 3 comprises two tire halves 6a, 6b arranged side by side in the axial direction and a respective radially extending tire endplate 7 with a central through-opening. A respective bearing flange 8 is fastened on the tire endplate 7. The two tire halves 6a, 6b are connected to one another so as to be rotatable about the rolling body axis via the two bearing flanges 8 and a spacer tube 9, by a bearing 10, for instance a roller bearing, being arranged between a bearing flange 8 and the spacer tube 9.

[0024] The swivel coupling 4 connected steerably to the superstructure 1 is connected elastically on both sides to a respective hollow hydraulic travel motor 12 via damping elements 11, for example rubber-metal elements, and a flange plate 39. On the output side the travel motors 12 are connected via a flange 13 to the adjacent bearing flange 8 and thus drive the respective tire halves 6a, 6b.

[0025] Situated in the center of the rolling body is an exciter shaft 14 which is driven by a hydraulic vibration motor 15 and is mounted opposite the bearing flanges 8 via bearings. An unbalance cylinder 16 is mounted centrally in a bore in the exciter shaft 14. For this purpose, the unbalance cylinder 16 has a corresponding collar and, on the opposite side, a threaded section for clamping by means of a clamping ring and a pair of nuts. The unbalance cylinder 16 accommodates an unbalance piston 17 such that it can be adjusted hydraulically radially with respect to the rolling body axis.

[0026] When changing the eccentricity by displacing the unbalance piston 17, the unbalance in the exciter shaft 14, which is sufficient to achieve the smallest nominal amplitude of the rolling body, can be added in an infinitely variable manner. The unbalance piston 17 may be filled with lead in order that where there is minimal construction space as large an adjustment range as possible for the nominal amplitude can be achieved.

[0027] The unbalance piston 17 is equipped with guide bands and a piston sealing ring. Deformations of the exciter shaft 14 (bending caused by centrifugal forces) are not transmitted to the unbalance cylinder 16, as a result of sufficient play. The required amount of oil for displacing the unbalance piston 17 is made available through a bore 18 in the exciter shaft 14. The oil pressure is transmitted to the head of the piston via a taper of the unbalance piston 17 and bores 19.

[0028] Situated in one of the bearing flanges 8 is an oil inlet and outlet nipple 20 for the purpose of lubricating the space within the spacer tube 9, and the adjacent bearings, etc.

[0029] As can be seen in FIG. 3, the pressurization of the unbalance piston 17 by means of an exactly metered amount of oil for displacing the unbalance piston 17 is performed via a rotary bushing 21 which, by virtue of rubber springs 22 and an additional vibrating mass 23, is suspended with low vibration on one of the travel motors 12. The vibrating mass 23 accommodates an adapter 24 which bears a piston 25 such that it can be displaced, the piston being connected via a tube 26 to a further piston 27 accommodated by the exciter shaft 14. Radial and axial displacements between the rotary bushing 21 and the exciter shaft 14 as a result of thermal expansions are compensated for by seals 28 of the pistons 25, 27. Pins 29 prevent rotational slip between the seals 28 and the exciter shaft 14 or the adapter 24 of the rotary bushing 21.

[0030] According to the embodiment shown in FIG. 4a, the required oil volume for changing the position of the unbalance piston 17 is metered by displacing an adjusting piston 34 of an actuating cylinder 40. Here, the piston rod 30 of the adjusting piston 34 is connected to a trapezoidal or ball screw drive 31 whose spindle is not displaceable (self-locking) under the action of tensile or compressive stress. The screw drive 31 is driven by an electric or hydraulic motor 32. An incremental travel measurement on the piston rod or, if appropriate, angular measurement on the screw drive 31 (preferably integrated therein and therefore not shown) is used to set the eccentricity of the unbalance piston 17 or the nominal amplitude. For the purpose of calibration and for leakage oil compensation, there is provided on the piston side an oil passage whose 2/2-way valve 33 can automatically be switched to the flow position as a function of the operating state.

[0031] According to the embodiment shown in FIG. 4b, the required oil volume for changing the position of the unbalance piston 17 using the adjusting piston 34 and its piston rod 30 is modified on the piston rod side by a variable oil volume. To this end, electromagnets of a 3/3-way valve 35 are activated cyclically in such a way that the adjusting piston 34 can be displaced by very small distances. When the 3/3-way valve 35 is pressure-connected, the adjusting piston 34 moves in the piston side direction and when tank-connected, because of the centrifugal force of the unbalance piston 17, in the piston rod side direction. The locking zero position of the 3/3-way valve 35 here replaces the self-locking action of the screw drive 31 of FIG. 4a. The sole function of the adjusting piston 34 with piston rod 30 here is incremental travel measurement for the purpose of setting the eccentricity of the unbalance piston 17 or the nominal amplitude. The calibration and leakage oil compensation correspond to those of FIG. 4a.

[0032] FIGS. 5a to 5c depict various positions of the unbalance piston 17 in combination with an adjusting device according to FIG. 4a (the same applies to the adjusting device of FIG. 4b). The unbalance piston 17 is in the position shown in FIG. 5a during the following four operating states:

[0033] 1. With the vibrating device at a standstill and the diesel engine running, the oil pressure at the unbalance piston 17 corresponds to the inlet pressure at the 2/2-way valve 33, which is fundamentally connected to flow in this operating state. As a result, the leakage oil quantity is replaced and at the same time the unbalance piston 17 is forced in the direction of smallest eccentricity against the "minimum unbalance" stop (calibration).

[0034] 2. The vibratory drive should be accelerated as quickly as possible with the lowest mass moment of inertia until the minimum operating frequency has been reached. Consequently, resonance ranges are rapidly passed through with the smallest nominal amplitude so that adjoining assemblies such as rotary swivel couplings 4 or superstructure 1 and their connections are only slightly stressed. When the minimum operating frequency has been reached, the 2/2-way valve 33 blocks the oil flow. Leakage oil replacement and calibration are automatically ended at the same time.

[0035] 3. The smallest nominal amplitude is set at the maximum vibrator frequency. The 2/2-way valve 33 is opened, with the result that leakage oil is replaced and calibration takes place.

[0036] 4. When the vibratory drive is switched off, the unbalance piston 17 automatically moves in the direction of smallest nominal amplitude in order to brake the vibratory drive with a small mass moment of inertia. As soon as the position of the adjusting piston 34 corresponds to that of FIG. 5a, the inlet pressure at the 2/2-way valve 33 is connected to flow. From this point in time, leakage oil can be replaced and the system calibrated.

[0037] The unbalance piston 17 is in the position shown in FIG. 5b only with the nominal amplitude set manually or automatically to maximum and with minimum operating frequency. The 2/2-way valve 33 is here connected to flow and the oil pressure corresponds to the inlet pressure of the directional valve. In this operating state, leakage oil can be replaced and the system calibrated. As soon as the adjusting piston 34 has reached the position of FIG. 5b, the 2/2-way valve 33 is immediately automatically closed. The nominal amplitude from this operating state can subsequently be reduced in an infinitely variable manner. The operating frequency is subject to follow-up control in the direction of smaller nominal amplitude, for example by means of characteristic map control, to avoid exceeding the permissible centrifugal force of the unbalance piston 17.

[0038] When the unbalance piston 17 is in the position shown in FIG. 5c, the 2/2-way valve 33 is closed and leakage oil replacement and calibration are not possible. The nominal amplitude can be increased or reduced in an infinitely variable manner from this operating state. The operating frequency is subjected to follow-up control in the direction of smaller nominal amplitude, as is the position of the unbalance piston 17 in the direction of larger nominal amplitude.

[0039] When the vibratory drive is switched off, the unbalance piston 17 is displaced from the positions shown in FIGS. 5b and 5c immediately in the direction of smallest nominal amplitude, independently of the decreasing operating frequency.

[0040] To achieve optimum soil or asphalt compaction, the vibration frequency is matched to the nominal amplitude, as described above. It is possible at the same time to automatically set the optimum rolling speed as a function of the vibration frequency and for this to be displayed to the roller driver. The position of the unbalance piston 17 can either be adjusted manually or automatically controlled as a function of the density (stiffness) of the ground. In tandem vibratory rollers, it is possible for either only the front or only the rear or for both rolling bodies 2, 3 to be fitted with an unbalance which can be adjusted in the manner described above.

[0041] In the embodiment shown in FIGS. 6a to 6c, a directional valve 35 is provided instead of the hydraulic motor 32 of FIGS. 5a to 5c, this valve being connected to the chamber of the actuating cylinder 34 on the piston rod side while the directional valve 33, in this case a three-way valve, is again connected to the chamber of the actuating cylinder 40 upstream of the adjusting piston 34.

[0042] In the embodiment shown in FIG. 6a, where the vibration is switched off after the adjusting piston 34 is completely retracted, the unbalance cylinder 16 is filled up with oil from the hydraulic source via a pump 37. For this purpose, at the same time as the vibration is switched off, the directional valve 33 is connected as shown in FIG. 6a. A pressure-limiting valve 36 is connected to the line from the pump 37 to the directional valve 33. If said valve 36 responds, this means that the unbalance cylinder 16 is completely filled with oil.

[0043] On reaching the state when the unbalance cylinder 16 is completely filled with oil, FIG. 6b, the directional valve 33 is switched over so that oil can flow back to the hydraulic source from the actuating cylinder 40, specifically from the chamber upstream of the adjusting piston 34, via a pressure-limiting valve 38, whereas the previously closed directional valve 35 is opened so that hydraulic oil can adjust the adjusting piston 34. Consequently, the quantity of oil in the adjusting cylinder 40 is returned completely to the hydraulic source, as a result of which the system is calibrated at the same time.

[0044] If this state is reached, the directional valves 33, 35 are closed and the vibration can be switched on, FIG. 6c. If then a certain frequency, for example 28 Hz, is reached, the amplitude is adjusted from the position of smallest amplitude shown in FIG. 6c by corresponding opening of the directional valve 35.

[0045] In this embodiment, apart from leakage oil replacement and calibration, there also simultaneously takes place an additional exchange of at least a large proportion of the total amount of hydraulic oil in the system comprising the cylinders 16 and 40 on each occasion that vibration compaction is stopped or interrupted. This is advantageous as regards ageing of the hydraulic oil and cooling thereof.

[0046] While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.

Claims

What is claimed is:

1. A compaction roller having at least one rolling body with a vibratory drive; the vibratory drive being turned on to produce a vibration having an amplitude and a frequency and comprising a drivable exciter shaft mounted axially within said rolling body, an external adjusting device, a control valve and a hydraulic oil source; the exciter shaft having an unbalance device comprising an unbalance cylinder and an unbalance piston; the unbalance cylinder being held by the exciter shaft, centrally with respect to the axis of the rolling body; the unbalance piston being hydraulically radially adjustable with respect to the axis of the rolling body; the adjusting device being in fluid communication with the unbalance cylinder through a bore in the exciter shaft, the adjusting device supplying hydraulic fluid in a controlled manner to infinitely variably adapt the amplitude of the vibration to paving situations; the adjusting device having an actuating cylinder and an actuating piston, the actuating cylinder defining a chamber, the actuating piston being disposed within the chamber, the chamber of the actuating cylinder being in fluid communication with the unbalance cylinder; an oil passage extending from the actuating cylinder to the hydraulic oil source, the control valve being disposed in the oil passage; the valve being moveable between open and shut positions, the valve shutting when the unbalance piston is in a radially central position, whereby moving the unbalance piston from the central position increases or decreases the amplitude of the vibration.

2. The compaction roller of claim 1, wherein the control valve shuts when the vibration has a minimum operating frequency.

3. The compaction roller of claim 1, wherein the control valve opens to provide fluid communication between the unbalance cylinder and the hydraulic oil source after the vibratory drive has been turned off.

4. The compaction roller of claim 3, wherein the control valve provides fluid communication between the actuating cylinder and the hydraulic oil source after the vibratory drive has been turned off.

5. The compaction roller of claim 3, wherein the actuating piston is moveable between extended and retracted positions within the actuating cylinder, the control valve being openable when the actuating piston is in the retracted position.

6. The compaction roller of claim 4, wherein the actuating piston is moveable between extended and retracted positions within the actuating cylinder, the control valve being openable when the actuating piston is in the retracted position.

7. The compaction roller of claim 5, wherein when the unbalance cylinder is filled with hydraulic oil, the actuating piston can be moved to the extended position.

8. The compaction roller of claim 6, wherein when the unbalance cylinder is filled with hydraulic oil, the actuating piston can be moved to the extended position.

9. The compaction roller of claim 1, the vibratory drive further comprising a rotary bushing connecting the unbalance cylinder to the adjusting device, the rotary bushing being supported on the rolling body by a damping element.

10. The compaction roller of claim 9, the vibratory drive further comprising a tube, a first piston disposed at a first end of the tube, and a second piston disposed at a second end of the tube, the first piston being axially moveably, rotationally fixedly connected to the rotary bushing, the second piston being axially moveably, rotationally fixedly connected to the exciter shaft.

11. The compaction roller of claim 1, wherein the actuating piston is mechanically or hydraulically adjustable.

12. The compaction roller of claim 11, wherein the vibratory drive further comprises sensory means for monitoring the position of the actuating piston.

13. The compaction roller of claim 1, the vibratory device further comprising means for measuring a compaction performance of the rolling body and means for controlling the adjusting device as a function of a measurement of the compaction performance of the rolling body.

14. The compaction roller of claim 1, wherein the unbalance piston is filled with a heavy metal.