DESCRIPTION OF PRIOR ART
[0001] In finishing machines for laying bituminous aggregates for modern road making, two
important parts are generally distinguished: a pulling part (tractor) and a part that
carries out the actual work of laying, levelling, compacting etc. the aggregate on
the road surface. The latter assembly, called a "screed", consists of an apparatus
which in the years has become very complex and articulated.
[0002] The most recent embodiments provide a screed composed of four distinct elements,
two central elements of which being articulated to each other and having systems for
adjusting the inclination of one element relative to the other. On each of these central
elements a stem element is mounted which is approximately equal in length to the other
elements and is horizontally slidable outwards, moved by hydraulic pistons.
[0003] This type of "screed" is generally called an "integrated screed" or "hydraulically
expandable screed".
[0004] The advantage inherent to the two expandable outer elements of the integrated screed
is that of being able to vary the laying width at will and without interruption. The
expandable side or outer elements may be fixed on the central elements in a variety
of ways depending upon the models and the types of finishing machines produced. Generally
very precise and rugged cylindrical guides are provided, in order to ensure that sliding
takes place respecting the geometric design characteristics of the "screed" element
as much as possible.
[0005] It is very important to respect said characteristics because the shape of the screed,
and especially its lower face, directly affects the resulting surface of bituminous
aggregate layed.
[0006] Even if the slide guides are made with high accuracy, there is always a danger that
the geometric shape planned for the road in fact suffers alterations due to elastic
deformations of the various members making up the "screed" when the expandable side
elements themselves are subject to considerable forces (static and dynamic reactions)
that occur with rapidly changing values during operation.
[0007] One of the most serious elastic deformations that usually takes place is torsional
strain which occurs, and can be detected, on the expandable side elements, which allow
rapid changing (at the wish of the road constructor and/or of the finishing machine
operator) of the laying width of the bituminous aggregate road coating.
[0008] In fact the expandable side elements with which this modem type of expandable screed
is provided must be constructed so as to be as light as possible, though assuming
a more or less parallelepiped shape, and therefore, for both these reasons, they are
difficult to implement in a sufficiently rigid structure to resist torsional stress.
[0009] On all known finishing machines to date, torsional stress in practice tends to deform
the expandable side elements, giving them a helical shape that is also transmitted
to the surface facing the roadway that is receiving the new coating of bituminous
material. This can have negative consequences on the perfection of the finished road.
[0010] This helical-shaped deformation is shown on the expandable side elements in a most
irregular fashion, depending upon the laying width that has been chosen to perform
the work. In other words, if the expandable side elements are pushed outwards as far
as possible, that is to the end of the stroke, each expandable element is hit completely
by the heap of material to be laid on the new roadway and therefore all reaction forces
act on the expandable side elements.
[0011] When an expandable side element has to work only partially pushed outward,on the
other hand, part of said expandable side element remains covered by a central element
of the screed, and is no longer in contact with the material to be laid; the reaction
forces acting on the expandable side elements are thus different or differently distributed.
[0012] It can therefore be stated that, depending upon the laying width to be achieved,
an expandable side element is subjected to different or differently distributed reaction
forces.
[0013] Consequently, an expandable side element will inevitably vary its own elastic deformation.
[0014] As has been seen above, the elastic deformation of the expandable side elements that
is of most concern is that which tends to twist said expandable side element.
[0015] If said expandable side element is considered similar to a parallelepiped with a
horizontally and transversally elongated shape, the deformation of most concern is
that which tends to cause the two vertical walls lying in the direction of forward
travel of the machine during work to rotate relative to each other.
[0016] When this happens, the horizontal surface that rests on the material to be spread
is helically deformed, causing considerable disturbance also on the surface of the
laid material.
[0017] Due to the inevitable elasticity of the materials with which these expandable side
elements can be made, and taking into account that, for intuitive reasons, these expandable
elements must be made so as to have their weight reduced as much as possible, in practice
it has been observed that, unfortunately, the above mentioned torsional deformations
or strains reach significant values however much care has been taken in making these
expandable side elements and their slide guides.
DESCRIPTION OF THE PRESENT INVENTION
[0018] A neat but approximate solution to combat and partially avoid these deformations
has been illustrated in Swiss patent CH 657 168 filed on 16.11.1982, which describes
a finishing machine the screed of which comprises central elements and expandable
side elements, and these can be individually preloaded by means of a preloading device.
[0019] Many hundreds of finishing machines have been built and put on the market provided
with "expandable screeds" made according to the aforementioned Swiss patent.
[0020] From the road yard experience observed during the work carried out by these machines
it could be noted that an even greater laying precision could have been achieved by
adopting construction materials and geometric shapes that allowed the torsional deformation
to be further reduced (something that modern technology has allowed as the years passed)
and at the same time introducing mechanical control means for more precise adjustment
of the relative position of the expanding side elements with respect to that of the
central elements of the screed.
[0021] Road yard experience has also shown that of three orthogonal directions to be kept
under control for adjusting the relative position of the expandable elements (with
respect to the position of the central ones), the most important is a polar rotational
direction with respect to a horizontal transversal axis that is as near as possible
(and in any case parallel) to the horizontal transversal geometric axis that contains
the bottom front edge of the central elements.
[0022] An object of the present invention is to allow the angular and vertical positioning
of an expandable element to be modified with respect to a corresponding central element
to compensate less approximately (than did the invention of the aforementioned Swiss
patent) for the elastic deformations caused on the entire screed by the reaction forces
that the bituminous aggregate exerts on the active surfaces of the screed during laying.
[0023] This object is reached with a finishing machine as stated in claim 1. Further new
and advantageous characteristics are said in the dependent claims.
[0024] The appended drawing schematically shows the main characteristics of the improved
finishing machine and precisely:
Figure 1 is a perspective diagrammatic rear view of a finishing machine provided with
a diagrammatically shown expandable screed forming the subject matter of the invention,
which is able to carry out gradual widening or narrowing of the coating of bituminous
aggregate to be laid on the road;
Fig. 2 shows an enlarged, partial and perspective rear view, of the left end of a
road surface laying device according to the invention in operating position with an
angle adjusting device acting on a left expandable side element; a second similar
(specular) angle adjustment device acts on a right expandable side element.
[0025] In the figures, reference F is a road surface finishing machine; M is a coating of
bituminous aggregate laid on the road.
[0026] The direction of travel of the finishing machine during the work is indicated by
the arrow Y.
[0027] In Fig. 1 a right expandable side element of the screed is indicated by 1 and a central
right element by 2 while the same elements on the left side are indicated by 1' and
2'.
[0028] In Figure 2 the element 1' has been illustrated partly broken off to improve understanding
of the inner structure.
[0029] Cylindrical guides 6 and 7, and also a stem 8 of an hydraulic actuator that transversally
slides expandable element 1', are mounted in a traditional manner (not shown) on the
corresponding central element (2') of the screed.
[0030] The guides 6 and 7 are mounted integral with the inner surface of an inner plate
9. Mounted on the same surface is an end of the stem 8 of the hydraulic actuator that
slides the expandable side element 1' with respect to the fixed central element 2'.
[0031] The plate 9 is mounted in a pack-like way by means of four through screws schematically
shown by 10 and 11 (two of these screws cannot be seen because they are coaxial with
the guides 6 and 7) with vertical body 12 of the expandable element 1'.
[0032] According to the present invention, between the vertical body 12 and the plate 9
is interposed an intermediate plate 13 (provided with large through holes - not visible
- to allow screws 10 and 11 to pass through) which is pivoted on body 12 by means
of a pivot 14, having a geometric axis of rotation indicated by straight line 14'.
[0033] The pivot 14 has a horizontal transversal geometric axis (with respect to the entire
finishing machine) disposed very near (and parallel) to the horizontal transversal
bottom front edge of the expandable element 1'.
[0034] The plate 13 carries two slide guides 15 (of which one is not visible in Figure 2
because it is hidden by the plate 9).
[0035] A screw-type or hydraulic adjustment device 16 of a known type engages on one side
plate 13 and on the other side a horizontal body 17 of the expandable element 1',
allowing angular adjustment of the plate 13 with respect to the element 1', causing
rotation around the pivot 14 and then, due to shape and orientation of the geometric
axis 14' of the pivot 14, around a horizontal transversal axis very near to the geometric
axis that contains the horizontal transversal bottom front edge of the expandable
element 1'.
[0036] Another screw-type or hydraulic adjustment device 18 of a known type engages on one
side on the plate 13 and on the other on the plate 9 to cause relative adjustment
thereof by sliding one plate with respect to the other in the direction imposed by
the guides 15.
[0037] All these adjustment movements obtained by acting on adjustment devices 16 and 18
are carried out when the four screws 10, 11 etc. are slightly loosened and the "pack"
formed by body 12, plate 13 and plate 9 has sufficiently low internal friction to
allow said adjustment movements.
[0038] During work, depending on the intensity of the stresses to which the expandable element
1' is subjected, the four screws 10, 11 etc. can be more or less tightly screwed so
as to ensure that the mutual positions which have been fixed acting on the two adjustment
devices 16 and 18 remain unchanged, until the changed working conditions induce the
operator to change said adjustments.
[0039] The expandable element 1' acts on the bituminous aggregate mix to be laid by means
of the bottom surface of its body 17 and the front surface of the plate 19 integral
with the bodies 12 and 17.
[0040] According to the present invention, by acting on the adjustment devices 16 and 18,
relative sub vertical and angular movements of the bodies 12 and 17 and of the related
active surfaces thereof are caused, with respect to the plate 9, consequently with
respect to the guides 6 and 7 and therefore with respect to the central element of
the screed 2'.
[0041] The object is thus achieved of modifying the angular and vertical positioning of
the expandable element 1' with respect to the corresponding central element 2' to
compensate, in a less approximate manner than was done with the invention of the aforementioned
Swiss patent, for the elastic deformations caused on the entire screed by the reaction
forces that the bituminous aggregate exerts on the active surfaces of the screed during
laying.
1. A road surface finishing machine (F) with a screed (1, 2, 1', 2') comprising central
elements (2, 2') of the screed and expandable side elements (1, 1') supported by transversal
guides (6, 7) slidably mounted on the central elements (2, 2') of the screed, an actuator
stem (8) that causes sliding of the expandable elements (1, 1') in a transversal direction
with respect to a direction of travel (Y) of the machine (F), characterized in that the expandable side elements (1, 1') comprise adjustment means for adjusting the
expandable side elements (1, 1') perpendicularly and angularly with respect to a worked
surface (M), said adjustment means comprises an inner plate (9) and an intermediate
plate (13), the intermediate plate (13) being mounted in a pack-like way by means
of screws (10, 11) with a vertical first body (12) of the expandable elements (1')
and being oriented generally perpendicular to the worked surface (M), the intermediate
plate (13) also being mounted rotatably around a pivot (14) having its geometric rotational
axis (14') integral with the first body (12), whilst the inner plate (9) is mounted
slidably along slide guides (15) integral with the intermediate plate (13).
2. A finishing machine according to claim 1, wherein said adjustment means further comprises
first and second screw-type or hydraulic adjustment devices (16, 18), said first adjustment
device (16) engaging between the intermediate plate (13) and the vertical body (12)
to cause an angular movement around the axis of the pivot (14), and said second adjustment
device (18) engaging between the intermediate plate (13) and the inner plate (9) to
cause a movement in a direction perpendicular to the worked surface (M) between the
inner plate (9) and the intermediate plate (13).
3. A finishing machine according to claim 1 or 2, wherein the adjustment means is mounted
on each of the expandable side elements (1 and 1') of the screed of the finishing
machine.
4. A finishing machine according to one of the preceding claims, wherein the geometric
axis of the pivot (14) is oriented paralle to the worked surface (M) , transversal
to the direction of travel (Y) of the finishing machine and substantially parallel
to a bottom edge of the expandable element (1') which is oriented in the front and
transversal with respect to the direction of travel (Y) and parallel to the worked
surface (M).
5. A finishing machine according to claim 1, wherein the geometric axis of the pivot
(14) is located adjacent to a bottom edge of the expandable element (1') which is
oriented transversal with respect to the direction of travel (Y) and parallel to the
worked surface (M).
6. A finishing machine according to claim 5, characterized in that the axis (14') of the pivot is parallel to the bottom edge of the expandable element
(1') which is oriented in the front and transversal with respect to the direction
of travel (Y) and parallel to the worked surface (M).
7. A finishing machine according to one of the preceding claims, wherein the rotation
of the inner plate (9) and the intermediate plate (13) relative to each other around
the geometric axis (14') is obtained by means adapted to make the inner or the intermediate
plate slide with respect to the other along rectilinear or curved guides, said guides
having contact surfaces which determine an instantaneous rotation axis coinciding
with the geometric axis (14').
1. Straßenflächenfertigungsmaschine (F )mit einem Schild (1, 2, 1', 2'), welches mittlere
Elemente (2, 2') des Schildes und ausfahrbare Seitenelemente (1, 1') aufweist, die
durch Querführungen (6, 7) getragen werden, die verschiebbar an den mittleren Elementen
(2, 2') des Schildes montiert sind, weiter mit einem Betätigungsvorrichtungsschaft
(8), der eine Verschiebung der ausfahrbaren Elemente (1, 1') in einer Querrichtung
mit Bezug zu einer Laufrichtung (Y) der Maschine (F) bewirkt, dadurch gekennzeichnet, daß die ausfahrbaren Seitenelemente (1, 1') Einstellmittel aufweisen, um die ausfahrbaren
Seitenelemente (1, 1') senkrecht und in Winkelrichtung mit Bezug zu einer bearbeiteten
Oberfläche (M) einzustellen, wobei die Einstellmittel eine innere Platte (9) und eine
Zwischenplatte (13) aufweisen, wobei die Zwischenplatte (13) in einer packungsartigen
Weise mittels Schrauben (10,11) montiert ist, wobei ein vertikaler erster Körper (12)
der ausfahrbaren Elemente (1') im allgemeinen senkrecht zur bearbeiteten Oberfläche
(M) orientiert ist, wobei die Zwischenplatte (13) auch drehbar um einen Schwenkzapfen
(14) montiert ist, der seine geometrische Drehachse (14') integral mit dem ersten
Körper (12) aufweist, während die innere Platte (9) verschiebbar entlang der Verschiebungsführungen
(15) integral mit der Zwischenplatte (13) montiert ist.
2. Straßenfertigungsmaschine nach Anspruch 1, wobei die Einstellmittel weiter erste und
zweite schraubenartige oder hydraulische Einstellvorrichtungen (16, 18) aufweist,
wobei die erste Einstellvorrichtung (16) zwischen der Zwischenplatte (13) und dem
vertikalen Körper (12) in Eingriff ist, um eine Winkelbewegung um die Schwenkachse
(14) zu bewirken, und wobei die zweite Einstellvorrichtung (18) zwischen der Zwischenplatte
(13) und der inneren Platte (9) in Eingriff steht, um eine Bewegung in einer Richtung
senkrecht zur bearbeiteten Fläche (M) zwischen der inneren Platte (9) und der Zwischenplatte
(13) zu bewirken.
3. Straßenfertigungsmaschine nach Anspruch 1 oder 2, wobei die Einstellmittel an jedem
der ausfahrbaren Seitenelemente (1 und 1') des Schildes der Straßenfertigungsmaschine
montiert sind.
4. Straßenfertigungsmaschine nach einem der vorhergehenden Ansprüche, wobei die geometrische
Achse des Schwenkzapfens (14) parallel zur bearbeiteten Oberfläche (M) orientiert
ist, wobei weiterhin die Querrichtung des Weges (Y) der Straßenfertigungsmaschine
und im wesentlichen parallel zu einer unteren Kante des ausfahrbaren Elementes (1')
orientiert ist, welches in der vorderen Richtung und quer mit Bezug zur Laufrichtung
(Y) und parallel zur bearbeiteten Oberfläche (M) orientiert ist.
5. Straßenfertigungsmaschine nach Anspruch 1, wobei die geometrische Achse des Schwenkzapfens
(14) benachbart zu einer unteren Kante des ausfahrbaren Elementes (1') gelegen ist,
welches quer mit Bezug zur Laufrichtung (Y) und parallel zur bearbeiteten Oberfläche
(M) orientiert ist.
6. Straßenfertigungsmaschine nach Anspruch 5, die dadurch gekennzeichnet ist, daß die Schwenkachse (14') parallel zur unteren Kante des ausfahrbaren Elementes (1')
ist, welches vor und quer zu der Laufrichtung (Y) und parallel zur bearbeiteten Oberfläche
(M) orientiert ist.
7. Straßenfertigungsmaschine nach einem der vorangehenden Ansprüche, wobei die Drehung
der inneren Platte (9) und der Zwischenplatte (13) relativ zueinander um die geometrische
Achse (14') herum durch Mittel erreicht wird, die geeignet sind, die innere Platte
oder die Zwischenplatte mit Bezug zu der anderen entlang geradliniger oder gekrümmter
Führungen gleiten zu lassen, wobei die Führungen Kontaktflächen haben, die eine sofortige
Drehachse bestimmen, die mit der geometrischen Achse (14') zusammenfällt.
1. Engin finisseur de route (F) comportant une table lisseuse (1, 2, 1', 2') comprenant
des éléments centraux de table lisseuse (2, 2') et des éléments latéraux extensibles
(1, 1') supportés par des guides transversaux (6, 7) montés à coulissement sur les
éléments centraux (2, 2') de la table lisseuse, une tige d'actionneur (8) propre à
entraîner le coulissement des éléments extensibles (1, 1') selon une direction transversale
à la direction de déplacement (Y) de l'engin (F), caractérisé en ce que les éléments latéraux extensibles (1, 1') comprennent des moyens d'ajustement pour
ajuster les éléments latéraux extensibles (1, 1') perpendiculairement et angulairement
par rapport à une surface traitée (M), les moyens d'ajustement comprenant une plaque
interne (9) et une plaque intermédiaire (13), la plaque intermédiaire (13) étant à
l'aide de vis (10, 11) montée en sandwich avec un premier corps vertical (12) des
éléments extensibles (1') et étant de manière générale orientée perpendiculairement
à la surface traitée (M), la plaque intermédiaire (13) étant également montée à rotation
par rapport à un pivot (14) ayant son axe de rotation géométrique (14') solidaire
du premier corps (12) tandis que la plaque interne (9) est montée à coulissement le
long de guides de coulissement (15) solidaires de la plaque intermédiaire (13).
2. Engin finisseur selon la revendication 1, dans lequel les moyens d'ajustement comprennent
également des premier et deuxième dispositifs d'ajustement hydrauliques de type à
vis (16, 18), le premier dispositif d'ajustement (16) étant relié fonctionnellement
entre la plaque intermédiaire (13) et le corps vertical (12) de manière à imprimer
un mouvement angulaire autour de l'axe du pivot (14), et le deuxième dispositif d'ajustement
(18) étant relié fonctionnellement entre la plaque intermédiaire (13) et la plaque
interne (9) de manière à imprimer un mouvement selon une direction perpendiculaire
à la surface traitée (M) entre la plaque interne (9) et la plaque intermédiaire (13).
3. Engin finisseur selon la revendication 1 ou 2, dans lequel les moyens d'ajustement
sont montés sur chacun des éléments latéraux extensibles (1 et 1') de la table lisseuse
de l'engin finisseur.
4. Engin finisseur selon l'une quelconque des revendications précédentes, dans lequel
l'axe géométrique du pivot (14) est orienté parallèlement à la surface traitée (M),
transversalement à la direction de déplacement (Y) de l'engin finisseur et sensiblement
parallèlement à un bord inférieur de l'élément extensible (1') qui est orienté vers
l'avant et transversalement à la direction de déplacement (Y) et parallèlement à la
surface traitée (M).
5. Engin finisseur selon la revendication 1, dans lequel l'axe géométrique du pivot (14)
est situé à proximité d'un bord inférieur de l'élément extensible (1') qui est orienté
transversalement à la direction de déplacement (Y) et parallèlement à la surface traitée
(M).
6. Engin finisseur selon la revendication 5, caractérisé en ce que l'axe (14') du pivot est parallèle au bord inférieur de l'élément extensible (1')
qui est orienté vers l'avant et transversalement à la direction de déplacement (Y)
et parallèlement à la surface traitée (M).
7. Engin finisseur selon l'une quelconque des revendications précédentes, dans lequel
la rotation de la plaque interne (9) et de la plaque intermédiaire (13) l'une par
rapport à l'autre autour de l'axe géométrique (14') est obtenue par des moyens aptes
à faire glisser la plaque interne ou la plaque intermédiaire l'une par rapport à l'autre
selon des guides rectilignes ou courbés, les guides ayant des surfaces de contact
qui déterminent un axe de rotation instantané coïncidant avec l'axe géométrique (14').