US20100278590A1

US20100278590A1 - Vibration plate having belt drive having multiple deflection

Info

Publication number: US20100278590A1
Application number: US12/810,046
Authority: US
Inventors: Otto W. Stenzel
Original assignee: Wacker Neuson SE
Current assignee: Wacker Neuson Produktion GmbH and Co KG
Priority date: 2008-01-18
Filing date: 2008-12-23
Publication date: 2010-11-04
Also published as: WO2009089899A1; CN101903597A; EP2245231A1; DE102008005066A1

Abstract

A vibration plate has an upper mass having a drive and a lower mass which is mounted so it is elastically moveable relative to the upper mass. The lower mass has a vibration generator and a ground contact plate. The drive is coupled by a belt drive to the vibration generator. The belt drive has a drive disk which is provided on the drive, an output disk which is provided on the vibration generator, and a belt which circulates between the drive disk and the output disk. To this end, at least two further deflection rollers are provided for guiding the belt.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a vibrating plate for soil compaction.
2. Description of the Related Art
Vibrating plates for soil compaction are known. They have an upper mass that includes the drive and a lower mass, flexibly movable relative thereto, having a soil contact plate and a vibration generator. In small and medium-sized vibrating plates, the transmission of force from the drive motor to the vibration generator takes place predominantly using a V-belt. The V-belt directly connects the pulley or V-belt disk on the motor shaft to the V-belt disk of the unbalanced generator.
In many vibrating plates, no device is provided with which the belt tension can be maintained or adjusted during operation. However, vibrating plates are also known that have a tension belt disk, often provided on the drive, in which, with the aid of a spring or an eccentric, the two V-disk plates of the belt disk can be pressed together axially, so that when there is low belt tension the reference diameter or pitch diameter of the belt disk is enlarged, while the reference diameter is reduced when the belt is strongly tensed. It is also known to press a tension roller from the inside against the V-belt at the return strand side in order to maintain the necessary tension at the return strand side.
Due to the action of the vibration generator and the unbalanced movement connected therewith, the distance between the upper mass and the lower mass changes with the frequency of the generator. In addition, the upper mass is excited to vibration in a number of different movement shapes (modes). In addition, during operation the operator exerts forces on the upper mass while guiding the vibrating plate, using a drawbar. While doing this, the operator presses the upper mass laterally or downward. It is also possible for the operator to pull laterally on the upper mass in order to achieve greater compaction on one side. This causes additional changes in distance between the upper mass and the lower mass. There also result errors of alignment between the belt disks at the drive side and at the driven side, as well as vertical and horizontal angular errors. The changes in distance, as well as the alignment and angular errors, have the result that the V-belt cannot circulate between the belt disks in the intended manner. Rather, its movement is significantly disturbed.
Further stress results from the non-uniform rotational movement of the drive motor, which in small and medium-sized vibrating plates is formed by a one-cylinder motor, and in larger vibrating plates is formed by a two-cylinder motor, or in rare cases by a motor having more cylinders. The eccentric shaft (unbalanced shaft) present in the vibration generator also stresses the V-belt via a non-uniformity that results from the kinetic energy exchange between the unbalanced shaft and the lower mass. The impact of the soil contact plate against the soil causes further fluctuations in rotational speed that cause stress to the belt.
Due to the numerous disturbing influences, the V-belt is sometimes insufficiently tensed, and then in the next moment is again excessively tensed. Superposed on this are strong forces resulting from the non-uniform rotational movement of the mutually interfering changes in rotational speed of the drive motor and of the vibration generator. This can cause the V-belt to slip at a certain point in time and in the next moment to be caught again in static friction. Due to these atypical stresses on the V-belt, the belt usually does not attain its intended useful life span.
The belt drive between the upper mass and the lower mass is generally provided only on one side of the vibrating plate. Thus, the V-belt tension and the tensile force of the return strand load the spring elements provided between the upper mass and the lower mass on one side. The resulting asymmetrical pre-tension of the spring elements, and the resulting asymmetrical spring rigidity, can have the effect that the vibrating plate travels on a curved path if it is not guided by the operator. Because of this, the operator must constantly take corrective action in order to achieve movement in a straight line.
FIG. 1 a shows, in a schematic side view, a known vibrating plate. FIG. 1 b shows a simplified mechanical equivalent diagram.
An upper mass 1 has a drive 2, e.g. a one-cylinder or two-cylinder internal combustion engine. On upper mass 1 there is provided a drawbar 3 with which the operator can guide the vibrating plate.
Upper mass 1 is coupled to a lower mass 4 in a known manner via spring devices or spring/damper devices (not shown). Lower mass 4 has a soil contact plate 5 and a vibration generator 6 situated thereon. On drive 2, a drive disk 7 is provided, while vibration generator 6 has a driven disk 8. Drive disk 7 is for example attached directly to the crankshaft of drive 2, while driven disk 8 is fastened to an extension of an unbalanced shaft of vibration generator 6. The drive energy is transmitted from drive disk 7 via a belt 9 to driven disk 8 and thus to vibration generator 6.
The design of this vibrating plate is known, so that further description can be omitted.

SUMMARY OF THE INVENTION

The present invention is based on the object of improving a belt drive for a vibrating plate in such a way that changes in distance between the upper mass and the lower mass, angular errors, and fluctuations in rotational speed impair the useful life of the belt less strongly.
According to the present invention, this object is achieved by a vibrating plate including an upper mass that has a drive and a lower mass that has a vibration generator and a soil contact plate, the lower mass being mounted so as to be flexibly movable relative to the upper mass. A belt drive couples the drive to the vibration generator. The belt drive has a drive disk provided on the drive, a driven disk provided on the vibration generator, and a belt that circulates between the drive disk and the driven disk. At least two additional deflecting rollers are provided for guiding the belt.
A vibrating plate having a belt drive that has a drive disk provided on a drive, a driven disk provided on a vibration generator, and a belt that circulates between the drive disk and the driven disk is characterized in that at least two additional deflecting rollers are provided for guiding the belt.
With the aid of the deflecting rollers, given skillful guiding of the belt it is possible to reduce the negative effects of the named disturbing influences such as the permanent changing of the distance between the upper mass and the lower mass, the angular error between the drive disk and the driven disk, and the fluctuations in rotational speed of the drive disk and of the driven disk. Thus, with the aid of the deflecting rollers it can be achieved that, as is explained in more detail below, the belt segments that run between the upper mass and the lower mass, i.e. elements (drive disk, deflecting roller mounted on the upper mass) that couple the upper mass to elements (driven disk, deflecting roller mounted on the lower mass) of the lower mass, run essentially horizontally and parallel to one another. In particular, changes in distance between the upper mass and the lower mass have only a slight disturbing effect as a result.
The deflecting rollers may be situated on the same side of an imaginary connecting line between an axis of rotation of the drive disk and an axis of rotation of the driven disk. In this way, it can be achieved that the belt is multiply deflected, and thus has a longer length that can better compensate the disturbing influences.
Those parts or segments of the belt that run between elements of the upper mass and elements of the lower mass, thus coupling the elements in question, can run essentially horizontal, or at an angle of less than 30° to the horizontal. In this way, changes in distance between the upper mass and the lower mass have only a slight effect. The part of the belt that runs around the deflecting rollers or deflecting disks changes its position only by a few angular degrees due to the horizontal run, so that its length changes only very slightly due to the cosine effect.
Depending on the specific embodiment, it is possible for the two deflecting rollers to be mounted on the upper mass, or for one deflecting roller to be mounted on the upper mass and one deflecting roller to be mounted on the lower mass. Here is possible to mount the deflecting rollers on an intermediate bank produced via a lever. It is also possible to situate both deflecting rollers on the lower mass, but this can be disadvantageous in view of the fact that significantly stronger vibrations are present on the lower mass.
In a specific embodiment, the vibrating plate is fashioned as a plate compactor plate. Plate compactor plates often have only a single unbalanced shaft, usually situated in the front area on the lower mass. Reversible vibrating plates are also known that have a vibration generator for the production of directed vibrations. Here, two or more rotatable unbalanced shafts that are positively coupled to one another so as to rotate in opposite directions are usually situated centrically on the lower mass.
If the vibrating plate is a plate compactor plate and has an unbalanced shaft in its front area, the deflecting rollers can be situated in a rear area of the vibrating plate. This makes it possible to achieve a very long horizontal run of the belt.
Depending on existing space conditions, it is possible also to form a deflecting roller by two (or more), usually smaller, deflecting rollers having smaller wrap angles. Thus, a deflecting roller having a wrap angle of 180° can be replaced by two deflecting rollers each having a wrap angle of 90°. Of course, arbitrary other wrap angles are also possible.
The distance between a deflecting roller of one bank and the drive disk or driven disk on the other bank, associated via the run of the belt and thus coupled to the deflecting roller, should be as large as possible. This makes it possible to effectively compensate changes in distance or angular errors. For example, the distance should be at least 20% of the length of the soil contact plate in the direction of travel.
The deflecting rollers can be situated such that a wrap angle at the drive disk and/or at the driven disk is greater than 180°. This makes possible an effective transmission of force between the disks and the belt.
At least one of the deflecting rollers can be mounted in displaceable or cardanic fashion along its axis of rotation. In this way, the offset and the tilt of the belt before and after the respective deflection roller can be averaged, which also results in destressing of the belt.
In a specific embodiment, one deflecting roller is mounted on the upper mass and one deflecting roller is mounted on the lower mass, those parts of the belt running between the upper mass and the lower mass running essentially parallel to one another. When there is a relative movement between the upper mass and the lower mass, in this way the changes in belt length are compensated.
A tension roller can be provided in order to tense a return strand of the belt.
In addition, or alternatively, a compensating roller can be provided for tensing a return strand of the belt.
The compensating roller can be held in a normal position by a spring device. Here, the pre-tension of the spring device can be dimensioned such that when a prespecified belt force is exceeded in the return strand, which wraps around the compensating roller at a particular angle, the compensating roller can be moved out of the normal position against the action of the spring device into a destressing position, so that the compensating roller yields to the belt force and the belt force acting in the return strand is reduced. In normal operation, the pre-tensioning force is not exceeded, so that the compensating roller acts as a rigidly mounted roller. If, however, in extreme situations (interference of several influencing quantities and accidental events, such as a stone caught between the belt and the disk) the permissible belt force is exceeded, the pre-tension force of the spring device is also exceeded. This moves the compensating roller out of the normal position and thus releases belt length, so that stress on the belt is relieved in the area of the return strand. The length of belt that becomes free should then be subsequently tensed by a tension roller in the return strand in order to maintain sufficient return strand tension for low-slippage operation.
The axes of rotation of the deflecting rollers can be inclined relative to the horizontal. This can be useful in particular if the deflecting rollers are to be situated as closely as possible next to one another, or even partly axially next to one another.
In a plate compactor plate it can for example be useful to situate the two deflecting rollers situated in the rear area next one another in order to lengthen the belt length that extends horizontally between the upper mass and the lower mass. If the deflecting rollers are inclined relative to the horizontal, they can be situated closely alongside one another. This causes the belt to be slightly twisted, but this is not a problem. The outer contour of the deflecting rollers can be made slightly convex in order to support the twisting. In addition, it can be useful if the drive disk and the driven disk are slightly offset relative to one another.
It is possible for the belt to be used, in addition to driving the vibration generator, also to drive an additional aggregate such as a ventilating fan, an auxiliary hydraulic system, or a current generator.
In addition, it is possible to provide more than two deflecting rollers in order to realize a still greater belt length. For example, four deflecting rollers may be provided; depending on the specific embodiment, two deflecting rollers are then situated in a front area of the vibrating plate and two deflecting rollers are situated in a rear area of the vibrating plate, or one deflecting roller is situated in the front area and three deflecting rollers are situated in the rear area, or three deflecting rollers are situated in the front area and one deflecting roller is situated in the rear area.
The axes of rotation of the deflecting rollers do not necessarily have to be parallel to one another. Rather, inclinations of the axes of rotation are also permissible, because twisting of the belt due to the complex movement pattern is possible and even desirable.
In a specific embodiment, one of the deflecting rollers is situated on the upper mass and one of the deflecting rollers is situated on the lower mass, the belt being guided in such a way that it circulates around the drive disk with its one side and around the driven disk with its other side. For this purpose, a belt must be provided that has profilings on both sides, such as a V-ribbed belt or a toothed belt. This results in a change in the direction of rotation between the drive and the vibration generator.
In this specific embodiment, the two deflecting rollers are situated on different sides of the imaginary connecting line between the axis of rotation of the drive disk and the axis of rotation of the driven disk. However, in this specific embodiment it is also to be provided that the parts of the belt that run between elements of the upper mass and the lower mass should be parallel to one another. This holds at least for the return strand.
In a specific embodiment, at least one of the deflecting rollers is mounted both on the upper mass and on the lower mass. Here, the mounting must be fashioned such that it is able to compensate the relative movement between the upper mass and the lower mass.
For this purpose, the relevant deflecting roller can be mounted on two lever elements, of which one is pivotably mounted on the upper mass and one is pivotably mounted on the lower mass. The lever elements run predominantly parallel to the respective stretches of belt running away from the relevant deflecting roller.
With the aid of this arrangement, it is possible to completely compensate the pre-tension forces of the belt. In this way, the belt tension does not pull the upper mass down on one side, so that the vibrating plate can travel in a straight line without additional corrective measures.
The mounting of the lever elements on the upper mass or lower mass can be realized in the form of joints. Due to the non-parallel movement of the upper mass and lower mass, they can be suspended in cardanic fashion. Alternatively, elastic elements may be used here.
The intermediate bank on which the deflecting rollers are fastened between the upper mass and the lower mass can also be fastened at least to one bank via systems of levers in the shape of parallelograms.
With the aid of the present invention, it is possible to use a belt that is as long as possible, in particular in the return strand, so that the forces that form in the belt due to fluctuations in the rotational speed remain small due to the elasticity of the long belt.
Due to a largely parallel guiding of the belt segments that couple the elements of the upper mass to the elements of the lower mass, and an identical direction of movement, changes in distance between the drive disk and the driven disk have almost no effect.
Cross-movements transverse to the belt guiding between the upper mass and the lower mass also have very little effect.
Given an essentially horizontal belt guiding between the two banks, angles of rotation about the central machine longitudinal axis essentially result only in a twisting of the belt, which the belt is able to withstand without damage. The translational displacement via the turning radius of the tilting movement in the vertical direction has almost no effect given a horizontal guiding of the belt.
The rotational movements of the upper mass about the vertical axis are of a low-frequency nature. They require a lengthening or shortening of the belt, which can be achieved by the named tension roller.
These and additional advantages and features of the present invention are explained in more detail below on the basis of examples with the aid of the accompanying Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows, in a schematic representation, a side view (a) of a known vibrating plate without the belt drive according to the present invention, as well as a mechanical equivalent diagram (b), both of which are labeled “Prior Art”;

FIG. 2 shows a belt drive according to the present invention;

FIG. 3 shows another specific embodiment of the belt drive;

FIG. 4 shows a rear view of FIG. 3;

FIG. 5 shows another specific embodiment of the belt drive;

FIG. 6 shows another specific embodiment;

FIG. 7 shows a further variant of the belt drive;

FIG. 8 shows yet another variant of the belt drive.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 shows, in a schematic side view, a highly simplified vibrating plate having a belt drive. In principle, the vibrating plate is similar to the vibrating plate described above on the basis of FIG. 1. Therefore, identical reference characters are used for identical components.
As FIG. 2 shows, belt 9 is guided not only around drive disk 7 (motor M) and driven disk 8 (generator E), but also around two deflecting rollers 10 mounted on upper mass 1 and around a deflecting roller 11 mounted on lower mass 4.
The two deflecting rollers 10 mounted on upper mass 1 can also be formed by a single deflecting roller whose wrap angle is then correspondingly larger.
Deflecting rollers 10, 11 are situated on the same side (in FIG. 2, the left side) relative to an imaginary connecting line 12 between the axes of rotation of drive disk 7 and driven disk 8.
Deflecting rollers 10, 11 are placed relative to disks 7, 8 in such a way that belt segments 9 a, which couple elements on different banks, run essentially horizontally. Thus, a belt segment 9 a is defined between drive disk 7 provided on the upper mass and deflecting roller 11 mounted on the lower mass, while the other belt segment 9 a runs between driven disk 8 provided on the lower mass and a deflecting roller 10 mounted on the upper mass.
The arrangement shown in FIG. 2 is suitable in particular for a reversible vibrating plate in which vibration generator 6, driven by driven disk 8, has two or more unbalanced shafts that are coupled to one another and that rotate in opposite directions, usually situated centrically on lower mass 4.
FIG. 3 shows a specific embodiment that is suitable primarily for a plate compactor, in which the unbalanced shaft (generator E) is usually situated well to the front on lower mass 4.
Here, two deflecting rollers are provided, namely a deflecting roller 10 mounted on upper mass 1 and a deflecting roller 11 mounted on lower mass 4. Here as well, belt segments 9 a run essentially horizontally between respective deflecting rollers 10, 11 and disks 7, 8 of different banks 1, 4.
As FIG. 3 shows, it is possible for the distance between a deflecting roller 10, 11 and the respectively associated disk 7, 8 of the other bank 1, 4 to be as large as possible. In this way, angular errors between the upper mass and the lower mass, or an offset, can be well tolerated. A long belt length ensures a larger degree of elasticity in order to mitigate the belt force peaks resulting from the rotational speed fluctuations. Additionally, or alternatively, it is possible for deflecting rollers 10, 11 to be mounted cardanically or so as to be displaceable longitudinally on their axis of rotation, so that the offset and the tilting on belt 9 before and after the respective roller 10, 11 averages out.
FIG. 4 shows a variant of FIG. 3, in a rear view from the right. FIG. 4 shows that the axes of rotation of deflecting rollers 10, 11 are inclined relative to the horizontal, and that deflecting rollers 10, 11 can be situated almost adjacent to one another, or at least closely alongside one another. In this way, the belt lengths of horizontal belt segments 9 a can be further extended somewhat. Here, belt 9 must be slightly twisted, which however does not present a problem over its length. The contour of deflecting rollers 10, 11 should be made slightly convex for this purpose. Drive disk 7 and driven disk 8 should be situated with a slight offset, as is shown in FIG. 4.
FIG. 5 shows a variant having four deflecting rollers, three deflecting rollers 10 being mounted on upper mass 1 and one deflecting roller 11 being mounted on lower mass 4. In this way, a still longer length of belt 9 can be achieved. Here as well, belt segments 9 a, which connect elements of the different banks 1, 4, can be situated horizontally.
FIG. 6 shows a variant in which, instead of a V-belt, a ribbed V-belt or a toothed belt having profiling on both sides can be used. Here, belt segments 9 b are provided that run essentially parallel to one another.
FIG. 7 shows an arrangement in which deflecting rollers 13 are mounted on upper mass 1 and on lower mass 4. For this purpose, each deflecting roller 13 is coupled via a lever element 14 to upper mass 1 and via a lever element 15 to lower mass 4. Lever elements 14, 15 run predominantly parallel to the respective belt stretches, i.e. to the partial segments of belt 9 that extend between the respective deflecting roller 13 and the associated disk 7, 8.
If the length of lever element 14, 15 is chosen to be equal to the free belt length in the relevant belt segment, the degree of parallelness to the belt segment essentially does not change when there is movement of the upper mass and the lower mass relative to one another. If their length is selected to be different, the error will be larger. However, it remains tolerable given small deviations.
FIG. 8 shows a variant similar to FIG. 7, in which deflecting rollers 13 press belt 9 inward, thus achieving a larger wrap angle of disks 7, 8.
A particular advantage of the arrangements shown in FIGS. 7 and 8 is that the pre-tension forces of belt 9 are completely compensated. Thus, the belt tension does not pull upper mass 1 and lower mass 4 together on one side. The embodiment shown in FIG. 7 permits a lengthening of belt 9 in the return strand, which is also shown by the arrows indicating the direction of rotation.
Due to the non-parallel movement of upper mass 1 and lower mass 4, it can be useful if lever elements 14, 15 on upper mass 1 or on lower mass 4 are suspended cardanically via joints. Alternatively, elastic elements may also be used for the mounting of lever elements 14, 15.

Claims

1. A vibrating plate comprising:

an upper mass that has a drive;

a lower mass that has a vibration generator and a soil contact plate, the lower mass being mounted so as to be flexibly movable relative to the upper mass; and

a belt drive that couples the drive to the vibration generator; the belt drive including

a drive disk provided on the drive;

a driven disk provided on the vibration generator; and

a belt that circulates between the drive disk and the driven disk; wherein at least two additional deflecting rollers are provided for guiding the belt.

2. The vibrating plate as recited in claim 1, wherein the deflecting rollers are situated on the same side of an imaginary connecting line between an axis of rotation of the drive disk and an axis of rotation of the driven disk.

3. The vibrating plate as recited in claim 1, wherein parts of the belt run between elements of the upper mass and elements of the lower mass and couple the elements of the upper mass to the elements of the lower mass and run essentially horizontally or with an angle less than 30° to the horizontal.

4. The vibrating plate as recited in claim 1, wherein:

both deflecting rollers are mounted on the upper mass; or

one deflecting roller is mounted on the upper mass and one deflecting roller is mounted on the lower mass.

5. The vibrating plate as recited in claim 1, wherein:

the vibrating plate is a plate compactor plate;

the vibration generator has an unbalanced shaft that is situated in an area that, seen in the direction of travel, is a front area of the vibrating plate; and wherein

the deflecting rollers are situated in a rear area of the vibrating plate.

6. The vibrating plate as recited in claim 1, wherein:

one deflecting roller is mounted on the upper mass and one deflecting roller is mounted on the lower mass; and wherein

parts of the belt run between the upper mass and the lower mass and run essentially parallel to one another.

7. The vibrating plate as recited in claim 1, wherein the rollers on the upper and lower masses are arranged in first and second banks, respectively, the distance between a deflecting roller of one bank and the drive disk, or driven disk, associated via the run of the belt, of the other bank is as large as possible.

8. The vibrating plate as recited in claim 1, wherein the deflecting rollers are situated in such a way that a wrap angle on at least one of the drive disk and the driven disk is greater than 180°.

9. The vibrating plate as recited in claim 1, wherein at least one of the deflecting rollers is mounted cardanically and/or so as to be longitudinally displaceable along its axis of rotation.

10. The vibrating plate as recited in claim 1, further comprising a tension roller that tenses a return strand of the belt.

11. The vibrating plate as recited in claim 1, further comprising a compensating roller that tenses a return strand of the belt.

12. The vibrating plate as recited in claim 11, wherein:

the compensating roller is held in a normal position by a spring device;

the pre-tension of the spring device is set such that when a prespecified belt force is exceeded in the return strand, the compensating roller moves the normal position against the action of the spring device, so that the compensating roller yields to the belt force and the belt force acting in the return strand is reduced.

13. The vibrating plate as recited in claim 1, wherein the axes of rotation of the deflecting rollers are inclined relative to the horizontal.

14. The vibrating plate as recited in claim 1, wherein the deflecting rollers are situated so as to be at least partly axially adjacent to one another.

15. The vibrating plate as recited in claim 1, wherein the belt is used to drive an additional aggregate.

16. The vibrating plate as recited in claim 1, wherein four deflecting rollers are provided,

two deflecting rollers being situated in a front area of the vibrating plate as seen in a direction of travel, and two deflecting rollers being situated in a rear area of the vibrating plate; or

one deflecting roller being situated in the front area and three deflecting rollers being situated in the rear area; or

three deflecting rollers being situated in the front area and one deflecting roller being situated in the rear area.

17. The vibrating plate as recited in claim 1, wherein:

one of the deflecting rollers is situated on the upper mass and one of the deflecting rollers is situated on the lower mass; and wherein

the belt is guided in such a way that its one side circulates around the drive disk and its other side circulates around the driven disk.

18. The vibrating plate as recited in claim 1, wherein at least one of the deflecting rollers is mounted both on the upper mass and on the lower mass.

19. The vibrating plate as recited in claim 18, wherein at least one deflecting roller is mounted on two lever elements, one of which is pivotably mounted on the upper mass and one of which is pivotably mounted on the lower mass.

20. The vibrating plate as recited in claim 18, wherein each of the lever elements is mounted cardanically and/or elastically on an associated one of the upper mass and the lower mass.