CA1050321A - Combination of a self-propelled vibratory roller and tired compacting roller - Google Patents

Abstract

A B S T R A C T

A self-propelled vibratory roller is shown in this disclosure. The roller provides an effective ground compaction.
The tire wheels in the compacting set transmit to the ground a force equal to the total weight of the roller unit divided by the number of wheels therein. The wheels are mounted to pro-vide an isostatic suspension for the unit. The roller includes means for blocking at least in one direction the oscillations transmitted to the tires relative to two tires located at the ends of the arrangement of tires in the roller unit. The tires are inflated with a pressure in the range of two to six atmos-pheric pressure. The distance between the axis of the vibratory and roller units is made less than four meters. The two units are connected by a steering articulation. The vertical axis of the articulation, when extended, will intersect the ground at a location equidistant from the projections on the ground of the axes of the two units.

Description

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This invantion relates to a combined type of vibratory-tired roller comprising in a single s01f-propelled machine having a plurality of compacting tires and a vibratory metal drum or cylinder.
It has been discovered that when using a single machine suitable to exert on the ground the static compacting action of the tire wheels and concuxrently the vibxatory action, a result is achieved which is by far higher ~han that provided b~ a conventional system using two separate self-propelled rollers, one of which heing a vibratory roller and the other a tired roller or the like. This surprising result is enhanced when the combined vibratory~tired roller is made to meet a series of structural and morphological conditions, as found by carrying out accurate ex-periments on road yards.
These structural and morphological conditions are as follows:
(a) All of the tire wheels are isostatically mounted, so that - each of the wheels will transmit to the ground a force equal to the total weight of the tixed machine unit divided by the number of wheels;
~b~ The isostatic suspension of the tire wheels can be blocked at least in one direction relative to the two tires located at the ends of the tire set;
(c~ The vibratory drum or cylinder operates on the ground at a distance not exceeding 4 m, with respect to the line of action for the set of the tamping tires;
(d) The weight relieved on the ground through the tires is higher than 50% of the total weight of the machine;
(e) The distance between each tire wheel and the adjoining one is less than the width of each tire wheel;

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(f~ The tire pressure ~s adjustable at least in the range of ~ ~ 6 atmospheres and accommodated to the ground nature;
(g) The tire diameter should be lar~er than 60% of the d~ameter vibratory metal drum or cylinder;
(h~ The articulation joining the two units, i.e. the vibratory and tired wheel units, has a vertical axis of rotation, the ideal extension of which intersects the ground in a point which is equidistant from the two projections on the ground of the axes of the two units (drum axis and tire wheel axis, respectively);
(i) The vibration frequency of the vibratory metal drum ranges between 20 and 40 Hz; and (1) The vibratory metal drum is suspended by pneumatic suspensions comprising pneumatic rings, each of which provided with at least two rigid elements embracing such rings, of which elements one is integrally mounted on the vibratory portion and the other integrally on the portion which should not vibrate, one of these two rigid elements being formed of at least two rigid segments which, when interconnected, will envelop and tighten the pneumatic ring, preventing it from any rotary motion and inhibiting the build-up of localized strains, while the other rigid element may be monolithic - of cylindrical shape, having two peripheral shoulder ribs.
Experimentally~ it could be shown that ~he compacting effect provided by a vibratory-tired machine concurrently meet-ing at least some of the above mentioned conditions is not only higher than that of two equivalent separate machines (one of which is only tired and the other only vibratory), but is also by far higher than that of other self-propelled combined machines not having the above characteristics.

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This surprising result provided ~y the machine accord~
ing to the present invention resides in that, as well known, the vibration reduces the inner friction of the material to be compacted so as to enable the ground granules to flow relative to one another, as if they have been immersed in a lubricating liquid In conventional self-propelled vibratory rollers some compaction action was provided, since, when being compressed, each granule would tend to be downwardly drawn by its own dead weight to fill up the voids in the soil, thereby increasing the density of the ground.
By adding the kneading and pressing action of a tire wheel inflated to the correct pressure to the dead weight of ; each granule, the compacting and stabilizing action is greatly accelerated, since the tire wheel will act on a material which is almost entirely free of inner frictions. However, care should be taken to prevent the tire wheel from tending to submerge into the material, that is to cause the material to flow ba~k and let the tire penetrate the ground. To this end, it was experimentally shown that an accurately defined balance should be maintained between the several load~ weight and size conditions of the various parts of the machine, or in other words, that at least some of the above mentioned conditions should be complied with.
Particularly, the condition setting the maximum 4 m.
distance between the operative zone of the vibratory drum and that of the compacting tires is considered essential in that within 4 m. radius the ground under vibration has such a decrease in inner friction that it enhances the compacting action of the tires, while i~ at a farther distance than 4 m., the vibration effect is no longer capable of sufficiently reducing the inner ~L~5~3;~.

friction to provide the above desirable tire kneading and compacting action~
The above results were shown in the following tests:
I Comparative test: Material to be compacted was a grave cement layer having a thickness of 20 cm.
Firstly, two machine units were used in which one of them was a self-propelled tired unit weighting 15-16 tons, having 7 tired wheels (11.00.20 section) with a load of about 2,200 kg for each wheel; and the other was a self-propelled vibratory lQ unit weighing 10 tons and formed of two vibrating drums 1.50 m.
wide with a vibration frequency adjustable between 30 and 40 Hz.
The two separate units were used simultaneously and kept as close to each other as possible.
On attaining the required density, higher than or equal to 95% of the modified Proctor, a maximum output of 130 m3/h could be achieved.
The same material was then treated with a composite machine weighing 15 tons, as a whole, and provided with four 11.00,20 section tired wheels, with 2,300 kg load per wheel, and havin~ a 1~50 m. wide vibratory drum with a frequency adjustable between 20 and 40 Hz, an output of 150 m3/h could be provided.
This composite machine met all of the ten above cited conditions.
II Comparative Test: Material to be compacted in this test was bituminous mlx having a final thickness o~ 15 cm~ Firstly, the material was treated with a vibratory roller weighing 6 tons and having a 1~25 m~ wide vi~ratory drum with a vibrati~n frequency of 35 Hz~, and a tired roller having seven 11~00.20 type of tire wheels, weighing 15 tons as a whole.
The required density at the completion of the rolling treatment was less than 5% voids.

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This predetermin~d density at the deepest zones of the layer could not be achieved by the use of the two separate machines.
The arrangement of the machines was then changed, placing the tired roller just behind the finishing machine, so as to operate on the still hot and plastic material, which was thus still readily compressihle.
An increased depth compaction was achieved, but the tired roller caused deformations and corrugations which the vibra-tory roller following the tired roller could not satisfactorily smooth out.
Therefore, it was required to add to the composite machine a third static road roller of the three metal wheel type in order to obtain a reasonable result both as to density and surface smoothness in the material treated.
III Comparative Test: Material to be compacted was Al type of ground according to AASHO regulations spread into a final layer of 50 cm, (after compaction~ The compacting operation was carried out by a self-propelled compacting or tamping machine of conven-`tional design and comprising two centrally articulated units.
One unit was a vibratory roller and the other was a push unit provided with two low pressure tire wheels.
Total weight of the machine: 9 tons Output power: 105 HP
Total applied force: 22 tons In order to achieve the desired 95% density of the modified Proctor, the conventional self-propelled tamper having the above features had to make 12 passes at a speed of 4 km/h.
The combined action self-propelled vibratory roller according to the present invention provided the same result with only 4 passes at the same speed, thus giving a per~ormance three ~ 5 -~0~iiO3'~1 times higher than that of the above d~scribed conventional machine.
The accompanying drawings show two embodiments of the combined machine according to the present invention, in which:
Figure 1 is a side view showing a combined full or double traction roller comprising a vibratory unit GV or a static unit GS, interconnected by a steering centrally ar~iculated joint, the distance between the drum and tired wheels axes being about 3 m.;
Figure 2 is a plan view of the machine shown in Figure l;
lQ Figure 3 is a rear view in the direction of arrows 10 and 20 of Figures 2 and 5, respectively;
Figure 4 is a side view of a second embodiment of the machine according to the invention, in which the vibratory unit GV does not have a driving unit for the vibratory metal drum (monotraction type);
Flgure 5 is a plan view of the machine shown in Figure 4;
Figure 6 is an enlarged sectional view taken along line VI-VI of Figure l;
Figure 7 is an enlarged sectional view taken along line VII-VII of Figure 3;
Figure 8 is an enlarged sectional view taken along line VIII-VIII of Figure 7; and Figure 9 is a sectional view taken along line IX-IX
of Figure 7.
The static unit GS is substantially the same both in the double traction design of Figures 1 and 2 and in the mono-traction design of Figures 4 and 5, Thls static unit comprises a frame 11 having an engine 12 and all the fittings for traction controls, as well as the plurality of tire wheels 13, rockingly mounted two by two and ~5~3'~
rotatable about the axis 14, whereas the oscillation of each pair of wheels for isostatic suspension is about the axes 15 and 16 (Figure 3).
The vibratory unit GV of the full traction design (Figures 1 and 2) is provided with a bearing frame 17, which is connected to the GS unit by a steering articulation 18, and accommodates the vibratory drum 19 supported by pneumatic vibration-damping suspensions.
The rotary traction motion is transmitted by the cardan ~ shaft 21 to the drive box 22 and therefrom to the vibratory drum 19.
The pneumatic vibration-damping suspensions are shown in Figure 6 which is a schematic sectional view through the drum 19.
The vibrating shaft 23 is shown as mounted on bearings 24 and rotated by the oleostatic engine 250 The large pneumatic ring 26 supports and insulates the right end of the vibratory drum, while its left end is supported and insulated by a plurality of pneumatic rings 27 as planet elements about the geometrical axis of the vibratory drum and coupled to a rotating element 28 which, in addition to support this end of the drum, is also capable of 2Q transmitting thereto the twisting movement for traction. All of the pneumatic rings 26 and 27 are surrounded by a cylindrical element 29 having peripheral ribs 30. On the other hand, each of the pneumatic rings 27 are internally embraced by a composite metal element 31. The air pressure within the pneumatic rings is ad-justable by means of common valves 32.
The isostatic assembling system for the tired wheels 13 of the static unit GS is shown in Figures 7, 8 and 9, wherein a pair of tires 13 are depicted. Each tire 13 rotates about its own axis 14 and is driven by a gear box 33 which imparts to the final shaft, coaxial with axis 14, the required torque for traction.

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At each pair of wheels, the frame 11 carries a sheet partition 34, on which are carried the two coaxial bearlngs 35, about which the box 33 along with the pair of wheels 13 and associated axis 14 can rock (Figure 8).
The oscillation angle is limited in both the right side and left side by a limiter device 36 having the function of right and left end o~ stroke.
An adjustable limiter dev.ice 37 (Figure 9) is also provided which comprises a nut screw 38 and a screw 39 externally operable by a key 40, The end 41 of the screw 39 can be pushed back and forward, as desired, to more or less restrict the oscil-lation of the reduction box 33 in one direction, but without restricting the oscillation thereof in the opposite direction.
This control is provided when the head 41 is adjusted to contact the abutment 42 of the gear box 33, Both of the two combined machines shown in Figures 1 and

2 and Figures 4 and 5, by way of example, have structural features that comply with the initially set forth conditions, and parti-cularly such conditions are:
- the tire wheels are isostatically suspended and provided with a locking device and its oscil~ation is restrictively controlled;
- the distance between a vertical line passing through the axis 13 and a vertical line passing through the axis o~ the vibratory drum 19 is 3 m.;
- the weight relieved on the ground through the plurality of tires 13 is about 2/3 the total weight of the machine, and thus higher than 50% of the latter, the distance between every two tire wheels 13 is less than the width of each tire wheel;
- the size and shape of the tires are such that the pressure can be adjusted in a range of 2 to 8 atmospheres;

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the diameter of the ~ires 13 is about ~5% f the diameter of the vibratory drum 19;
the vertical axis of the articulation 18 is equidistant from the two axes of rotation for the tire wheels and vibratory drum l9;
the vibration frequency of the drum can be adjusted in a range of 20 to 40 Hz.;
the suspensions for insulati.ng the vibration transmission of the vibratory drum are of the pneumatic ring type surrounded by circumferentially ribbed rigid elements.

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Claims (6)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A composite machine for ground compacting including a self propelled vibratory roller and a compacting unit, wherein said vibratory roller comprises a bearing frame and a vibratory metal drum mounted to said frame through pneumatic vibration damping suspensions, and said compacting unit comprises a plurality of wheels which are operative to provide a compacting force on the ground equal to the total weight of said compacting roller divided by the number of wheels, comprising means adapted for blocking at least in one direction any oscillations manifested by two lateral end wheels of said plurality of wheels, said plurality of wheels being pneumatic wheels inflated with a pressure in the range of two to six atmospheric pressure, and the axes of said vibratory metal drum and said pneumatic wheels being spaced apart in a distance of less than four meters, said vibratory roller and said compacting roller being interconnected by a steering articulated joint, whose pivot is located in a vertical line which intersects the ground at a location equidistant from two vertical lines passing through the central axes of said vibratory drum and said pneumatic wheels respectively.

2. A composite machine according to Claim 1, wherein said pneumatic tamping tired wheels have a diameter larger than 60% of the diameter of said vibratory metal drum.

3. A composite machine according to Claim 1, wherein the weight exerted on the ground by said pneumatic tamping tired wheels is higher than 50% of the total weight of the machine.

4. A composite machine according to Claim 1, 2 or 3, wherein the space between the adjoining pneumatic tamping tired wheels is less than the width of each wheel.

5. A composite machine according to Claim 1, 2 or 3, wherein said vibratory drum in said vibratory roller is operated at a vibration frequency in a range of 20 to 40 Hz., and is journalled on its rotational axis by pneumatic rings, each of said rings being provided with at least two rigid enveloping elements in which one enveloping element is mounted integrally on said rotational axis and the other enveloping element is formed integrally on a bearing frame, said one enveloping element comprising two rigid segments interconnected together to envelop and tighten the associated pneumatic ring and forming a unitary element therewith, said other enveloping element being cylindrical in shape and having a horizontal axis provided with two peripheral shoulder ribs adapted to engage the outer side of the associated pneumatic ring.

6. A method of compacting ground by using a self propelled vibratory drum followed at a distance of no more than 4 meters by a tamping unit, wherein said unit includes a plurality of pneumatic tamping tired wheels and exerts to the ground a force equal to the total weight of said unit divided by the number of tired wheels therein, comprising setting a spacing between said vibrating drum and said tamping tired wheels to a distance of less than four meters, providing an articulated joint interconnecting said self-propelled vibratory drum and said tamping unit for relative horizontal swinging movement, and positioning the articulated joint with the pivot located in a vertical line which intersects the ground at a location equidistant from two vertical lines passing through the axes of said vibratory drum and said series of parallel wheels respectively, inflating said wheels to a pressure in the range of two to six atmospheric pressure, and blocking at least in one direction any oscillations manifested in two lateral end wheels of said unit during compacting operation.