IMPACT COMPACTOR

DISPOSITIF DE COMPACTAGE PRODUISANT DES PERCUSSIONS

English Abstract

The invention concerns an impact compactor (10) which comprises one or more
out-of-round compactor masses (14). The masses
are moved rotationally over a soil surface, at an angular velocity suitable
for normal operation, to apply periodic compaction blows to the
soil surface. This is achieved by primary drive means. In the case of a towed
impact compactor, the primary drive means is typically a
tractor. The impact compactor (10) includes an auxiliary drive which is
arranged to operate automatically, in response to a reduction of the
angular velocity of the compactor masses below the angular velocity suitable
for normal operation, to apply an auxiliary rotary drive that
restores their angular velocity.

French Abstract

L'invention se rapporte à un dispositif de compactage produisant des percussions (10) et comportant une ou plusieurs masses de compactage disposées en faux-rond. Ces masses se déplacent de manière rotatoire à la surface d'un sol, et à une vitesse angulaire convenant à un fonctionnement normal, dans le but d'appliquer des percussions périodiques à la surface du sol et ce, grâce à un élément de commande principal. Lorsque l'invention concerne un dispositif de compactage produisant des percussions remorqué, l'élément de commande principal est généralement un tracteur. Ledit dispositif (10) comporte une unité de commande auxiliaire qui est conçue pour fonctionner automatiquement en réponse à une réduction de la vitesse angulaire des masses de compactage à une vitesse inférieure à la vitesse angulaire convenant à un fonctionnement normal, le rôle d'une unité de commande rotatoire auxiliaire étant de rétablir la vitesse angulaire desdites masses.

Claims

-8-
CLAIMS:
1. An impact compactor comprising at least one out-of-round
compactor mass which in use is movable rotationally by primary
drive means, at an angular velocity suitable for normal
operation, over a soil surface to apply periodic compaction
blows to the soil surface, the impact compactor including
auxiliary drive means arranged to operate automatically, in
response to a reduction of the angular velocity of the, or
each, compactor mass below an angular velocity suitable for
normal operation, to apply an auxiliary rotary drive to the, or
each, compactor mass to restore its angular velocity to that
suitable for normal operation.
2. An impact compactor according to claim 1 wherein the
auxiliary drive means comprises a hydrostatic drive powered by
the primary drive means and control means, which is responsive
to the angular velocities of the compactor mass and of driven,
ground engaging wheels of the primary drive means, for
controlling the operation of the hydrostatic drive.
3. An impact compactor according to claim 2 wherein the
hydrostatic drive comprises an hydraulic motor powered by an
hydraulic pump which is driven in use by the primary drive
means, the hydraulic motor being arranged to drive the, or
each, compactor mass by chain drive means.
4. An impact compactor according to claim 3 wherein the
control means comprises a proportional valve which regulates
the flow of hydraulic fluid from the hydraulic pump to the
hydraulic motor under the control of a sensor and associated
electronics sensitive to the angular velocities of the
compactor mass and of driven, ground engaging wheels of the
primary drive means.

-9-
5. An impact compactor according to either one of claims 3 or
4 comprising a pair of spaced apart compactor masses mounted
fast on a common shaft for synchronous rotation.
6. An impact compactor according to claim 5 wherein the
compactor masses are mounted on hubs at the ends of the common
shaft and the chain drive means comprises a first sprocket
driven by the hydrostatic motor, a chain passing about the
first sprocket and about a second sprocket fast on an auxiliary
shaft and means for driving the hubs off the auxiliary shaft.
7. An impact compactor according to claim 6 wherein the means
for driving the hubs off the auxiliary shaft comprises third
sprockets fast with the auxiliary shaft and meshing with fourth
sprockets fast with the hubs.
8. An impact compactor according to any one of claims 1 to 7,
the impact compactor is hitchable in use to a tractor which
serves as the primary drive means.
9. An impact compactor according to any one of claims 1 to 7
wherein the impact compactor incorporates its own primary drive
means.

Description

CA 02290465 1999-11-15
WO 98/51866 PCT/GB98/01400
- 1 -
IMPACT COMPACTOR
BACKGROUND TO THE INVENTION
THIS invention relates to impact compactors.
The term "impact compactor" refers to a soil compaction machine which
incorporates a rotatable, out-of-round mass that produces a series of impact
blows to the soil surface when towed or otherwise driven over that surface.
The compactor mass of an impact compactor has multiple sides defin.i.ng a
series of spaced apart salient points on its periphery, each salient point
being
followed by a compacting face. As the mass is towed or otherwise driven
ovcr the soil surface, it rises up on each salient point and then falls
forwardly and downwardly as it passes over that point, with the result that
the following compacting face applies an impact blow to the soil surface.
The action of the mass is therefore to store potential energy as it rises up
on
each salient point and then to deliver this energy as an impact blow.
Impact compactors as described above have been found to work well in
practice in achieving high levels of soil compaction, even at substnntial
depths below the soil surface. Problems may however be encountered in
situations where the salient points tend to dig in or slide relative to the
soil
surface, with the result that the rotational speed of the compactor mass is
reduced below normal levels, adding resistance to forward motion of the
impact compactor. The problem can be compounded in situations where the
impact compactor incorporates a traiiing levelling blade to level the
compacted soil, because the inclusion of a levelling blade also increases the
resistance to forward motion of the impact compactor.

CA 02290465 1999-11-15
WO 98/51866 PCT/GB98/01400
- ~ -
SU;NIlYIARY OF THE INVENTION
According to the present invention there is provided an impact compactor
comprising at least one out-of-round compactor mass which in use is
movable rotationally by primary drive means, at an angular velocity suitable
for normal operation, over a soil surface to apply periodic compaction blows
to the soil surface, the impact compactor including auxiliary drive means
arranged to operate automatically, in response to a reduction of the angular
velocity of the, or each, compactor mass below an angular velocity suitable
for normal operation, to apply an auxiliary rotary drive to the, or each,
compactor mass to restore its angular vclocity to that suitable for normal
operation.
Although otlier types of auxiliary drive are within the scope of the
invention,
the preferred auxiliary drive means comprises a hydrostatic drive powered
by the primary drive means and control means, which is responsive to the
angular velocities of the compactor mass and of driven, ground engaging
wheels of the primary drive means, for controlling the operation of the
hydrostatic drive. The hydrostatic drive conveniently comprises an hydraulic
motor powered by an hydraulic pump which is driven in use by the primary
drive mcans, the hydraulic motor being arranged to drive the, or each,
compactor mass by chain drive means. In this arrangement, the control
means may comprise a propon.ional valve which regulates the flow of
hydraulic fluid from the hydraulic pump to the hydraulic motor under the
control of a sensor and associated electronics sensitive to the angular
velocities of the compactor mass and of driven, ground engaging wheels of
the primary drive means.

CA 02290465 1999-11-15
WO 98/51866 PCT/GB98/01400
- 3 -
The invention extends to a dual mass impact compactor comprising a pair
of spaced apart compactor masses mounted fast on a common shaft for
synchronous rotation. In this case, the compactor masses are typicatly
mounted on hubs at the ends of the common shaft and the chain drive means
comprises a first sprocket driven by the hydrostatic motor, a chain passing
about the first sprocket and about a second sprocket fast on an auxiliary
shaft and means for driving the hubs off the auxiliary shaft. Such means may
conveniently comprise third sprockcts fast with the auxiliary shaft and
meshing with fourth sprockets fast with the hubs.
BRIEF DESCRIPTION OF 'THE DRAWINGS
The invention will now be described in more detail, by way of example
only, with reference to the accompanying drawings in which:
Figure 1 shows a perspective view of the chain drive and
associated components of an auxiliary drive
arrangement of an impact compactor according to the
present invention, with the chain itself omitted in the
interests of clarity of illustration;
Figure 2 shows a partially diagrammatic plan view of the chain
drive and associated components seen in Figure 1;
Figure 3 shows a partially diagc'aminatic side view of the chain
driven and associated components seen in Figurc 1;

CA 02290465 1999-11-15
WO 98/51866 PCT/GB98/01400
- 4 -
Figure 4 diagrammatically illustrates an impact compactor
which incorporates the chain drive and associated
components of the preceding Figures.
DESCRIPTION OF A PREFERRED EMBODINIENT
Figure 4 diagrammatically illustrates an impact compactor 10 according to
the invention. In this case, the impact compactor 10 is arrarnged to be towed
by a prime mover in the form of a tractor 12, but it will be understood that
the invention is also applicable to impact compactors which are self-
propelled, i-e. which incorporate their own prime mover.
In this embodiment, the impact compactor 10 includes a pair of three-sided
compactor masses 14 of conventional design. The masses 14 are mounted
fast on a common shaft 16 which forms part of a tube axle assembly 18 seen
in plan in Figure 2. The tube axle assembly 18 includes a tube 20 to which
a draglink 26 is connected, as illustrated. As shown diagrammatically in
Figure 4, the dragiink 26 is connected by a droplink 28 (Figure 4) to a
wheeled carriage 30 which is hitched to the tractor 12.
Those skilled in the art of impact compaction will recognise that the towed
impact compactor 10, as thus far described, is of conventional design. It will
also be appreciated that the traction assembly including the draglink and
droplink is resilient in nature to absorb shock loading when the compactor
masses are towed over the soil surface and apply impact blows thereto.
Reference may be made to the disclosure in, for instance, WO 94/26985 for
further details of the traction assembly for the compactor masses.

CA 02290465 1999-11-15
WO 98/51866 PCT/GB98/01400
- 5 -
What is not conventional about the impact compactor 10 is the inclusion of
an auxiliary drive arrangement. This arrangement includes a positive
displaccment hydraulic motor 32 mounted on a mounting plate 33 connected
to the draglink 26, and a chain drive indicated diagrammatically in Figure
4 by the numeral 35. Referring to the more detailed views of Figures 1 to
3, the chain drive includes a sprocket 34 mounted on the output shaft of the
motor 32. A chain 36, represented diagrammatically in Figures 2 and 3 by
a broken line, passes around the sprocket 34 and around a sprocket 38
mounted on a shaft 40 which is parallel to and above the shaft 16 and which
is supported in inner and outer bearings 42 and 44 carried by the tube 20 of
the tube axle assembly 18.
The ends of the shaft 40 carry sprockets 46. Further chains 47 pass around
the sprockets 46 and around sprockets 48 connected to hubs 50 on which the
compactor masses 14 are mounted. The masses 14 are omitted from Figures
1 to 3 in the interests of clarity of illustration. The chain drive 35 also
includes chain tensioners 52, 53 and 54 to maintain proper tension in the
chains 36 and 47 and an idler sprocket assembly 56.
Referring again to Figure 4, the motor of the tractor motor is indicated with
the reference numeral 58 and the transmission with the numeral 60. Driven
wheels of the tractor are indicated with the numeral 62.
A variable displacement hydraulic pump 64 of conventional swash plate type
is driven off the transmission 60. The pump 64 supplies hydraulic fluid to
the motor 32 under the control of a proportional valve 66 coupled to a
sensor and associated electronic control (not shown) sensitive to the
rotational, i.e. angular velocity, of the masses 14 and the driven whecls 62.

CA 02290465 1999-11-15
WO 98/51866 PCT/GB98/01400
- 6 -
In normal operation, hydraulic fluid is pumped continuously to the motor 32
by the pump 64. If the sensor senses a rotational velocity mismatch between
the compactor masses and the driven wheels 62, i.e. the wheels turn faster
than the compactor masscs, the valve 66, under electronic control, increases
the rate of flow of hydraulic fluid to the motor 32. Via the chain drive
mechanism, the hydraulic motor 32 accordingly exerts additional rotational
torque on the compactor masses and accelerates them rotationally so that
their rotational velocity catches up with that of the wheels 62.
A velocity mismatch may, for instance, occur if one or other of the
compactor masses digs into or slips relative to the soil surface rather than
rotating about the next salient point, indicated in Figure 4 with the numeral
68, or if the action of a trailing levelling blade, indicated diagrammatically
in Figure 4 with the numeral 70, should excessively increase resistance to
forward motion of the impact compactor-
As soon as the velocities have been matched again, the vatve 66 decreases
the supply of hydraulic fluid to the motor 32 to normal levels, and norrnal
progress of the compactor masses resumes.
It will thus be appreciated that the impact compactor 10 has a hydrostatic
drive control which automatically supplies extra rotary power to the
compactor masses in the event of a velocity mismatch.
The sprocket 38 is mounted on the shaft 40 via a unidirectional clutch 72
which transmits rotary motion in one direction only and which freewheels
in the other direction.

CA 02290465 1999-11-15
WO 98/51866 PCT/GB98/01400
- 7 -
With this feature, it is not possible for the compactor masses to drive the
tractor should their rotational speed exceed that of the wheels 62. This may,
for instance, happen when the masses fall forwardly as they pass over the
salient points.
In the above description the auxiliary drive is hydrostatic in nature. However
it should be appreciated that the principles of the invention are equally
applicable to other forms of auxiliary drive, including purely mechanical or
clectro-mechanical arrangements. The chain drive could be replaced by any
other suitable system including, for instance, independent hydraulic drives
at the hubs of the compactor masses. It should also be noted that the
invention is not limited in scope to use with towed compactor masses and
is equally applicable to self-propelled impact cornpactors incorporating their
own prime movers.

Representative Drawing