This application claims the priority of European Application EP08021844.9 filed Dec. 16, 2008, which is incorporated herein by reference in its entirety.
The invention relates to a paving screed and to a method for carrying a paving mat of variable working width.
More precisely the invention relates to a road paver paving screed, comprising: a base screed and extension screeds respectively supported by guiding assemblies in an extension guiding structure at a guidance fixed at the base screed, which extension screeds are arranged at the front side or the rear side of the base screed and are retractable and extendable in a sliding direction by means of drives relative to the base screed for varying the working width of the paving screed, sole plates respectively arranged at the lower sides of the base screed and of the extension screeds, connections arranged at the base screed for towing bars for floatingly towing the paving screed with an angle of attack of the sole plates relative to a planum, a respective multiple point suspension provided at the guiding assemblies between the extension guiding structure and the base screed, a frame in the extension screed, the frame carrying the sole plate of the extension screed, and at least two substantially vertical adjustment assemblies, which are spaced apart in the sliding direction of the respective extension screed, the adjustment assemblies engaging at the extension guiding structure at least for adjusting the height position of the frame relative to the base screed via at least one drive, a lateral inclination adjustment assembly having at least one remotely controlled drive, the lateral inclination adjustment assembly being structurally separated from the adjustment assemblies for adjusting a slope inclination angle at the sole plate of the extension screed relative to the base screed about a pivot hinge having a hinge axis oriented at least substantially perpendicular to the sliding direction and parallel to the sole plate of the extension screed.
Furthermore, the invention relates to a method for laying a paving mat of variable working width on a planum and comprising a lane and at least one laterally inclined, sideward slope with a paving screed comprising a base screed having a sole plate and at the front side or the rear side of the base screed at least one extension screed having a sole plate arranged at a frame for forming the slope outside of a transition from the lane into the slope, the extension screed being retractable and extendable laterally relative to the base screed for varying the working width, the extension screed being retractable and extendable together with an extension guiding structure at a base screed guidance having several guiding assemblies, at least two adjustment assemblies spaced apart in sliding direction and engaging at the extension guiding structure for adjusting the height position of the sole plate of the extension screed relative to the sole plate of the base screed, and a lateral inclination adjustment assembly being structurally and functionally separated from the adjustment assemblies for adjusting in the extension screed a lateral inclination angle of the sole plate of the extension screed in relation to the base screed for forming the slope, the method comprising the steps of towing the paving screed on the paving material, varying the working width and adapting at least the height position of the extension screed sole plate relative to the base screed sole plate corresponding to a variation of the working width.
During the production of a paving mat which is laterally continuous over the working width the working width is varied by extending or retracting the extension screeds relative to the base screed. A variation of the angle of attack of the floatingly towed paving screed (e.g. according to U.S. Pat. No. 4,379,653 A or DE-C-27 09 435) relative to the planum, which angle of attack influences the thickness of the paving mat, needs to adapt the height position of the rear edge of the respective sole plate of an extension screed relative to the rear edge of the sole plate of the base screed. This is executed by actuating the adjustment assemblies. A laterally varying thickness of the paving mat is achieved by adjusting different height positions of the towing points of the towing bars of the paving screed at the road paver. In this case, unavoidably, the base screed undergoes significant torsion. Despite the torsion of the base screed it has to be assured that the extension screeds can be uniformly retracted and extended for varying the working width. In addition, dragging forces and friction forces caused by the paving material then act on each extension screed sole plate, an edger plate and/or a screed extension part mounted at the outer end of the extension screed. These additional forces and the torsion both hinder uniform extensions or retractions of the extension screed. Among others frequently paving mats are produced in Northern America which paving mats have a lane and at least one sideward downwardly inclined slope. In this case the sole plate of one extension screed is inclined laterally in the travelling direction. It is then important to maintain the transition between the lane and the slope in lateral direction stationary with respect to the base screed when the working width is varied.
The paving screed known from U.S. Pat. No. 4,379,653 A has in one embodiment (FIGS. 1 to 16) the adjustment assemblies for the height position of the sole plate of the extension screed and the lateral inclination adjustment assembly functionally combined and arranged between the extension guiding structure and a front wall of the base screed. The extension guiding structure is a dual tube guiding frame. In the embodiment of FIGS. 17 to 24, to the contrary, the adjustment assemblies provided for adjusting the height position of the sole plate of the extension screed relative to the base screed are functionally and structurally separated from the lateral inclination adjustment assembly. The lateral inclination adjustment assembly is provided between a mounting bracket arranged at the rear side of the front wall of the base screed and the front wall of the base screed. The extension guiding structure is a dual tube guiding frame anchored at the mounting bracket and abuts at the front side of the front wall of the base screed. The height position of the extension guiding structure is adjustable relative to the mounting bracket by means of scissor lever adjustment assemblies supported at the mounting bracket. The frame of the extension screed is fixedly mounted at the extension guiding structure. All weight forces of the extension screed and also the dragging resistance of the paving material are transmitted exclusively via the mounting bracket into the base screed, as the extension guiding structure is movably arranged in abutting relation at the front wall of the base screed. The extension screed is supported counter to the travelling direction only on two small ring surfaces at the front side of the front wall of the base screed. Unavoidable torsions of the extension screed caused by the towing bars, the dragging resistance and the weight forces tend to bend the long guiding rods received in the two guiding tubes of the extension guiding structure. This partly or totally hinders small and/or rapid and smooth extension or retraction movements of the extension screed. The loose arrangement of the extension screed at the front wall of the base screed with the front wall clamped between the mounting bracket and the extension guiding structure, furthermore, hinders precise and rapid adjustments of the height position of the sole plate of the extension screed during the retraction or extension of the extension screed, which adjustments would be needed to hold the transition between the planar lane and the slope stationary with respect to the base screed, because the width of the lane should not change when the working width is varied.
The adjustment assemblies in the extension screed of the paving screed known from DE-C-2709435 both serve to adjust the height position and the lateral inclination of the sole plate of the extension screed. Adjustments of the lateral inclination are carried out here for forming certain crown profiles on the surface of the paving mat. The adjustment assemblies may have the form of spindles or hydrocylinders and may be remotely controlled also depending on the angle of attack of the base screed. In order to assure in case of a torsion of the base screed and/or when the working forces are acting that the working width can be varied without jamming, the multiple point suspensions of both extension screeds are statically defined three point suspensions of the extension guiding structures which thus cannot jam while being extracted or retracted.
In the paving screed known from DE-U-92 11 854 the sole plates of the extension screeds are automatically adjusted relative to the base screed to the respectively needed height position corresponding to the respective angle of attack of the paving screed relative to the planum, such that the formation of longitudinal steps is prevented in the surface of laid paving mat. This is carried out by implementing a regulating process. The paving screed contains a three point suspension for the extension guiding structure at inner and outer cheeks of each extension screed, in order to allow to vary the working width without jamming of the extension screeds despite significant forces.
The paving screed known from CH-B-488863 has at least one extension screed at the base screed and allows among others to lay paving mats having a sideward downwardly inclined slope. The extension screed is pivoted at the guidance which is fixed at the base screed either about a pivot axis which is substantially parallel to the planum and extends in travelling direction, or the guidance itself is pivoted together with the extension screed about the pivot axis at the base screed. In the first case a variation of the working width automatically also changes the lateral position of the transition between the lane and the slope. This is a significant drawback because then the width of the lane also varies. In the second case the transition remains stationary with respect to the base screed when the working width is varied. However, for pivoting the guidance at the base screed very complicated structures are needed.
The paving screed known from U.S. Pat. No. 5,568,992 has extension screeds which are mounted via extension guiding structures at the rear side of the base screed at guidances which are fixed in the base screed. The paving screed can also be used for producing a paving mat having at least one sideward downwardly inclining slope. By use of the adjustment assemblies of each extension screed then both the height position of the sole plate of the extension screed and the lateral inclination are adjusted. For a height adaptation both adjustment assemblies are adjusted synchronously and for the same stroke. For adjusting a lateral inclination angle of the sole plate of the extension screed both adjustment assemblies are adjusted over different strokes. A regulating system, to which different relevant information e.g. from sensors is transmitted, automatically regulates the simultaneous actuation of both adjustment assemblies such that with a variation of the working width the vertical position of the extension screed is changed in response to the angle of attack of the base screed so that a certain alignment is maintained between the base screed and the extension screed while the transition between the lane and slope is maintained stationary with respect to the base screed.
WO-A-2004/081287 discloses a paving screed in which each extension guiding structure moves on four support points of two parallel guiding tubes. Due to unavoidable torsions of the base screed and of the high reaction forces caused by the paving material this four point suspension tends to jam when the working width is varied of the base screed and also in case of high reaction forces caused by the paving material.
The paving screed known from US-A-2007/0258769 has extension screeds mounted at guidances at the front side of the base screed. Each extension screed has two adjustment assemblies for both height adaptations of the sole plate of the extension screed and adjustments of the lateral inclination angle. Each extension screed is sub-divided like a telescope into two sections. When the sole plate of the extension screed is inclined laterally relative to the base screed the guidances are pivoted accordingly.
Further prior art is contained in U.S. Pat. No. 592,489.
Paving screeds having extension screeds should not exceed a certain transport width corresponding to the width of the base screed. Furthermore, it is desirable to achieve a maximum working width substantially corresponding to the twofold width of the base screed. For these reasons each extension screed of the paving screed known from EP-B-1031660 can be extracted for about the half width of the base screed which comprises two base screed halves. A guiding fixation which is fixed to one base screed half is arranged for the extension screed such that the guiding fixation extends from one base screed half beyond the middle of the base screed into the other base screed half. Thereby a guiding body connected to the extension screed can be slid beyond the middle of the base screed into the other base screed half, when the extension screed is going to be fully retracted. This does not only result in a maximum working width corresponding substantially with the twofold width of the base screed, but advantageously also allows to stably suspend the maximally extended extension screed. The multiple point suspension of the extension guiding structures is a three point suspension which cannot jam when the extension screed is retracted or extended despite torsions of the base screed and/or high acting reaction forces caused by the paving material.
It is an object of the invention to provide a structurally simple and robust paving screed for laying a paving mat even having a slope, and to provide a method which can be carried out with this paving screed, such that in the case of a variation of the working width the transition between the slope and the lane can be held stationary with respect to the base screeds in a simple fashion. In particular when forming the slope high working forces should neither influence the retraction or extension of the extension screed nor the quality of at least the surface of the laid paving mat.
This object is achieved by the invention described herein.
As both adjustment assemblies in the paving screed exclusively are used for the height adaptation of the sole plate of the extension screed, while the angle of the lateral inclination of the sole plate of the extension screed is adjusted structurally separate about the pivot hinge relative to the frame or at the frame, for both functions simple and reliable adjustment assemblies and driving systems and control systems may be used. The structurally and functionally separated lateral inclination adjustment assembly also can be constructed simply and stably. The control for actuating the adjustment assemblies and/or the lateral inclination adjustment assembly can be simple when these assemblies are actuated separately. In particular, the adjustment assemblies can be actuated relatively rapidly in order to maintain the lateral position between the lane and the slope with respect to the base screed relatively precisely stationary when the working width is varied. As the adjustment assemblies only carry out height adjustments, and as the lateral inclination adjustment assembly only sets the lateral inclination, the respective adjustment processes may be coordinated relatively simply. As the adjustment assemblies are arranged between the extension guiding structure and the lateral inclination adjustment assembly facing the sole plate of the extension screed, the extension guiding structure is retracted and extracted in a sliding direction which is fixed with respect to the base screed. During movements the extension guiding structure is stably suspended in the multiple point suspension such that the extension guiding structure does not jam. All weight forces and also the dragging resistance of the paving material are transmitted via the extension guiding structure into the base screed, such that the lateral inclination adjustment assembly at least partially remains free from such forces. The lateral inclination of the adjustment assembly is functionally acting independently of the transmission of these forces into the base screed exclusively between the adjustment assemblies and either the sole plate of the extension screed or the frame carrying the sole plate of the extension screed.
According to the method the lateral inclination angle of the sole plate of the extension screed is adjusted independently from the adjustment assemblies provided for height adaptations only. For each height adaptation operation both adjustment assemblies of the extension screed do not need to be actuated individually. The transition remains stationary by use of a simple control, and optionally by a common drive for the adjustment assemblies.
In an embodiment of the paving screed working forces of the paving material acting at the frame deviate the sole plate of the extension screed and are directly transmitted to the extension guiding structure via the adjustment assemblies and via optionally provided vertical guidances, such working forces may become relatively high in the case when a slope is formed. The inclined sole plate of the extension screed remains free of such high forces, resulting in a good surface quality of the paving mat in the region of the slope. The suspension and the adjustment of the inclination of the sole plate of the extension screed in the frame only need simple structures which operate with low wear.
Expediently, the lateral inclination adjustment assembly has the pivot hinge either at the frame or at an intermediate frame, and as a drive at least one actuator which is distant in sliding direction from the pivot hinge. For adjustments of the lateral inclination angle moderate forces will then suffice to achieve a well-defined pivot movement. An inclination angle which normally is only set once is maintained reliably during the laying of a paving mat. The adjustment assemblies are always actuated over the same strokes and thus withstand working forces better and therefore are apt to follow a retraction or extension of the extension screed rapidly enough in order to hold the lateral position of the transition stationary. The adjustment assemblies engage at the frame if the sole plate of the extension screed is inclined laterally relative to the frame, or engage at the intermediate frame if the frame carrying the sole plate is inclined laterally relative to the intermediate frame.
Expediently, the sole plate of the extension screed is a planar plate having a skirt which extends upwardly along one longitudinal front side of the plate. In order to relieve the sole plate of the extension screed as much as possible from dragging forces caused by the paving material during the laying of a paving mat, expediently a front wall is mounted at the frame at the front side of the frame, seen in travelling direction. The front wall extends from above downwardly in front of the skirt of the sole plate of the extension screed, which skirt is then hidden behind the front wall, such that a part of the working forces from the paving material acting at the front wall are directly transmitted into the frame. Furthermore, the front wall hinders that paving material forming a high heap floats over the skirt and contaminates the extension screed.
A carrying frame is arranged on the sole plate of the extension screed when the sole plate is to be inclined laterally relative to the frame. The carrying frame, preferably, can be removed. The carrying frame comprises parts of the pivot hinge and at least one support for the actuator. The frame, preferably, has an inverted U-shaped cross-section with an open lower side which is closed by the sole plate, and carries further parts of the pivot hinge and a support for the actuator. This is advantageous because the sole plate of the extension screed is a wear part that in this case can be exchanged easily. Furthermore, the carrying frame fitted from below into the frame stiffens the sole plate of the extension screed.
The hinge axis may be defined by at least one pin which is inserted into the aligned parts of the pivot hinge. The pin supports the sole plate of the extension screed stably and over a significant width at the frame or supports the frame in the same manner at the intermediate frame.
Expediently, a mounting plate is arranged at the outer end of the frame. The mounting plate serves to mount either an edger plate or a screed extension part for setting an even larger working width. Forces which result e.g. from the dragging resistance of a screed extension part or the edger plate in the paving material act in the frame and deviate the sole plate of the extension screed.
In an embodiment of the paving screed having the extensions screeds mounted to the front side or to the rear side of the base screed the lateral position of the pivot hinge can be selected arbitrarily. In each case it is of advantage if the actuator has a large distance in sliding direction from the pivot hinge. An extension screed mounted to the front side of the base screed is working in travelling direction ahead of the base screed. In this case there is no danger that paving material may accumulate in front of the base screed when a slope is formed. If the extension screeds are mounted at the rear side of the base screed, the actuator may, preferably, be arranged in an end region of the frame facing towards the middle of the base screed, while the pivot hinge may be arranged in the end region of the frame which is remote from the middle of the base screed. In this case the sole plate of the extension screed is pivoted at its end facing towards the base screed about the hinge axis which is placed as far as possible to the outer side. This assures that when forming a slope no triangular dead space will be formed in front of the extension screed where paving material could accumulate.
The actuator of the lateral inclination adjustment assembly is at least one hydrocylinder which is oriented substantially vertically or is a hydraulically or electrically driven spindle drive which e.g. by internal friction or hydraulic blockage safely holds the selected lateral inclination angle. In order to carry out a sensitive adjustment with moderate driving force the actuator may, preferably, be combined with an angular transmission or a worm drive converting the rotary motion of the actuator into the adjustment movement. For stability reasons even two actuators may be provided which are distant from each other in travelling direction.
As the working forces resulting from the paving material and acting mainly at the outer end of the frame may be markedly high, specifically when extension screed parts are mounted, it may be expedient to functionally associate vertical guidances to the adjustment assemblies. Universal joints may be provided between the vertical guidances and the frame. If the frame is not inclined laterally for adjusting the lateral inclination of the sole plate of the extension screed, the vertical guidances even could be connected rigidly with the frame. However, even then universal joints may be expedient when the frame is inclined laterally or is tilted, in order to adjust the angle of attack of the extension screed individually from the angle of attack of the base screed, as may sometimes be necessary.
In an expedient embodiment with the sole plate of the extension screed being inclined laterally relative to the frame the lower side of the frame and the upper side of the skirt of the sole plate of the extension screed should rise gradually in sliding direction towards the middle of the base screed. In this case, preferably, the inclination of the lower side of the frame may limit a maximum lateral inclination angle of about 10%. When the sole plate of the extension screed is then inclined laterally with the maximum lateral inclination angle, it comes to a mechanical stop and is supported stably.
As when laying a paying mat with a slope at least the base screed may undergo torsion due to different elevation settings of the towing points of the towing bars of the paving screed, and when relatively high working forces have to be expected, it may be expedient to design the multiple point suspension as a three point suspension which cannot jam even in case of torsion of the base screed. The extension guiding structure has a first support point at an outer cheek outside of the base screed at a telescope tube which is extendable and retractable in a telescopic tube arrangement of the guidance fixed in the base screed. The extension guiding structure has a displaceable second support point at an inner cheek within the base screed and on the telescope tube. Furthermore, a guiding rail is fixed at the rear side of the extension guiding structure. The guiding rail extends in sliding direction and engages slidably into a torque support fixed at the base screed. The torque support supports the guiding rail in both rotary directions about the axis of the guidance and such that the guiding contact between the torque support and the guiding rail defines a third support point. This three point suspension operates in the case of torsion of the base screed without jamming such that the working width can be varied as rapidly as needed and very uniformly. However, this type of the three point suspension dictates that each extension screed can be extended only with a stroke which does not correspond to the full half width of the base screed, such that the maximum working width does not correspond to the twofold width of the base screed. This also puts a limit on the width of the slope formed by the fully extended extension screed.
In order to allow to produce an optimum width of the slope and a maximum working width of the paving screed substantially corresponding to the twofold width of the base screed when both extension screeds are maximally extended, in a further expedient embodiment the multiple point suspension of the extension guiding structure also is a three point suspension operating in the case of torsion of the base screed without jamming. In this case the extension guiding structure has the first support point at an outer cheek outside of the base screed at a telescope tube which can be extracted and retracted in a telescopic tube arrangement of the guidance fixed at the base screed. An inner cheek of the extension guiding structure has a displaceable second support point in a guiding body on a guiding tube. The guiding tube is fixed in the base screed parallel to the guidance and with an offset in travelling direction. Furthermore, a guiding rail fixed at the rear side of the extension guiding structure and extending in sliding direction defines a third support point where it engages in a torque support fixed at the rear side of the base screed. The guiding tube is secured at an inner end in the base screed in a fixation which extends from the side of the extension screed beyond the middle to the other side of the base screed such that the guiding body defining the second support point may travel on the guiding tube beyond the middle of the base screed substantially towards the fixation when the extension screed is maximally retracted. This structure results in a maximum extension stroke of the extension screed corresponding to half of the width of the base screed, such that by using both extension screeds a working width can be set which corresponds substantially to the twofold width of the base screed. Even in the case of a torsion of the base screed and with exterior forces acting from the paving material a rapid variation of the working width is possible while at the same time, e.g. in co-action with the adjustment assemblies the transition into the slope is held stationary. Owing to the placement of the fixation securing the guiding tube in the respective other side of the base screed it may be expedient to place at least the two guiding tubes in the base screed with a lateral offset such that the fixations do not interfere with each other.
A further embodiment of the paving screed allowing a largely automatic or at least semi-automatic remote actuation of adjustment operations, or allowing comfortable adjustment operations executed by the operator of the road paver or by personnel, has a lateral inclination measurement device for measuring the lateral inclination of the sole plate of the extension screed and/or a height measuring device for measuring the relative height difference between the sole plate of the extension screed and the sole plate of the base screed and/or a linear travelling measuring device within or at the actuator the lateral inclination adjustment assembly, each connected in signal transmitting fashion with a superimposed control device. With the help of information on the actual conditions the extension screeds can be adjusted rapidly enough, such that irrespective of variations of the working width during laying of a paving mat with a slope the transition between the lane and slope will be held stationarily with respect to the base screed, or at least when drifting off is returned relatively rapidly to the desired lateral position.
In an embodiment of the paving screed in which the frame is inclined laterally together with the sole plate of the extension screed and relative to the intermediate frame, it may be expedient to arrange the adjustment assemblies at the intermediate frame in sliding direction of the extension screed between the pivot hinge and the actuator of the lateral inclination adjustment assembly. This structure results in an optimally large support length for the frame at the intermediate frame. Even a mounted screed extension part will also be inclined laterally so that a broader slope can be formed.
In order to hold the transition between the lane and the slope with respect to the base screed stationary when the working width is varied, remotely controlled adjustment assemblies are obligatory, such that the height adjustments can be carried out while the extension screed is retracted or extended. Each adjustment assembly may comprise at least one screw spindle device or a hydrocylinder and a drive. Expediently, even a common remotely controlled drive is associated to both adjustment assemblies of each extension screed. A common drive is structurally simple and assures the synchronous adjustment of both adjustment assemblies respectively over the same stroke. The drive may be a hydraulic or even an electric drive. Expediently, a chain drive or chain drives or transmission trains are provided between the respective drive or the common drive and the respective screw spindle device. The common drive could even engage at only one screw spindle device which then is coupled by a chain drive with the other screw spindle device in order to achieve synchronous adjustments of both screw spindle devices. In order to distribute loads uniformly occurring during rapid height adjustments, it may be expedient to provide in each screw spindle device of one adjustment assembly a pair of screw spindles and to drive the screw spindles of the pair synchronously. The respective vertical guidance expediently then may be arranged between both screw spindles of the pair. In this case both screw spindles may be arranged in travelling direction one behind the other.
According to the method it may be advantageous if a variation of the lateral inclination angle of the sole plate of the extension screed needed during the laying of a paving mat is executed exclusively by actuation of the lateral inclination adjustment assembly which is arranged in the frame, while at the same time the adjustment assemblies are actuated separately in order to hold the lateral position of the transition with respect to the sole plate of the base screed stationary.
A control routine or regulation routine may be implemented according to which the height adjustment speed of the adjustment assembly is correlated as a guiding parameter with the speed of the retraction or extension of the extension screed. This may mean that, e.g., the speed of the extension or retraction in sliding direction is matched with the adjustment speed of the height adjustment corresponding to the set lateral inclination angle.
At least two adjustment assemblies 3 are arranged substantially vertical with a distance in-between in sliding direction Z between an extension guiding structure A1 at the guidance F which is fixed to the base screed G and the sole plate 2 of the extension screed A (
When laying the paving mat 43 the paving material V, e.g. bituminous paving material or concrete paving material, is poured onto the planum P from the road paver RF in front of the paving screed E, is spread out laterally by a not shown lateral distribution device, and is levelled and compacted by the paving screed E which floats on the paving material V. Optionally, additional tampers, vibrators and/or pressing assemblies at or on the sole plates 1, 2 may level and compact the paving mat 43. The lane 45 formed by the base screed G is planar in lateral direction or has a crown profile. If the towing points 5 are set to different elevations (the thickness of the paving mat varies in lateral direction) the base screed G undergoes torsion via the fixedly connected towing bars 9 such that the angle of attack α varies in lateral direction.
The base screed G may, according to
The extension screed A can be slidably retracted or extended at the guidance F which is fixed in the base screed G via an extension guiding structure A1 by means of e.g. one drive 14 (e.g. a hydraulic cylinder) and parallel to the base screed G (sliding direction Z in
The first guiding assembly F1 (
The second guiding assembly F2 includes a guiding rod or a guiding tube 12′ which is parallel to the telescopic tube arrangement in the base screed part G1 and is fixed between the cheeks 15, 16. The right side end of the guiding tube 12′ in
The third guiding assembly F3 includes in
The three point suspension with the support points P1, P2, P3 assures that the extension screed A moves over the full stroke without any jamming.
In case of two extension screeds A, here arranged at the rear side of the base screed G, both extension guiding structures A1, and the guidances or guiding assemblies F1, F2, F3 are designed equally. However, the guiding assemblies F1, F2, F3 are offset to each other in the base screed parts G1, G2 in a side view of the paving screed E in order to prevent mutual collisions when both extension screeds A are fully retracted.
The most important advantage of the three point suspension of the extension guiding structure A1 is that in case of torsion of the base screed G and also in case of torques imparted by the paving material V on the extension screed A jamming do not occur such that the displacement drive 14, the cylinder tube 12 of which extends from the base screed part G1 beyond the middle M into the other base screed G2 may vary the working width rapidly and without jerks or blockages which otherwise would result in undesirable faults in the surface of the laid paving mat 43.
Another type of a three point suspension is also indicated in
In each case the guiding body 17, 17′ is connected such with the inner cheek 18 that it may travel through a cut-out portion in the outer cheek 16 of the base screed part G1, and such that the extension guiding structure A1 may move through this cut-out into the base screed part G1 until the outer cheek 29 abuts at the outer side of the outer cheek 16.
The two adjustment assemblies 3 provided per extension screed A include e.g. two screw spindle devices 30, 31 (
In
Alternatively, a separate drive 20 e.g. a hydraulic motor or an electric gear motor, could be provided for each screw spindle 32 or for each screw spindle device 30, 31.
The lateral inclination adjustment assembly Q is arranged in the frame A2 and includes a remotely actuable actuator 22 (e.g. a hydraulic motor, hydraulic cylinder or an electric motor) which e.g. (schematically indicated in
The sole plate 2 of the extension screed A can be pivoted by means of the actuator 22 about the hinge axis X of a pivot hinge 21 in the frame A2 in order to set the lateral inclination angle 39′. In the shown embodiment, in which the extension screed A is mounted at the rear side of the base screed G the hinge axis X is situated e.g. at the outer end region (close to the mounting plate 46 in
Either an edger plate 48 or a screed extension part 49 may be mounted at the mounting plate 46 at the outer end of the frame A2. The edger plate 48 forms a sideward boundary of the poured paving material V. The screed extension part 49 allows to lay a paving mat with even larger working width. The dragging resistance of the paving material V imparts forces on the frame A2, in particular via the edger plate 48 and/or the screed extension part 49. These forces deviate the sole plate 2 of the extension screed A and are introduced along a force transmission path within the frame A2 and via the vertical guidances 33 and the adjustment assemblies 3 into the extension guiding structure A1.
The frame A2 of the extension screed A in
The sole plate 2 of the extension screed A has the shape of a planar plate and at a front side an upwardly bent skirt 38′. The sole plate 2 carries a trough-shaped carrying frame 59 (which is welded on and/or fixed by threaded connections) carrying bearing blocks 58 as further parts of the pivot hinge 21. The carrying frame 59, furthermore, has the support 47 for the actuator 22. The skirt 38′ has an upper edge 52 which first extends parallel to the sole plate 2 and then extends in a further portion obliquely upwards. A front wall 51 is mounted at brackets 50 on the frame A2. The front wall 51 extends downwardly to an inclined lower edge 53 and overlaps the skirt 38 (in travelling direction R in front of the skirt 38′) in order to take up forces from the paving material V and to shield a marked part of the skirt 38′.
In a not shown alternative of the paving screed E (front mount version) each extension screed A may be mounted at the front side of the base screed G by means of a guidance F fixed in the base screed and of an extension guiding structure A1 analogous to
In this case the hinge axis X or the pivot hinge 21 may be positioned close to the inner end region of the frame A2 or even somewhere between the end regions of the frame A2. In this case the actuator 22 e.g. can be positioned in the vicinity of the outer end region of the frame A2.
The height of the frame A2 gradually decreases e.g. corresponding to the maximum lateral inclination angle 39, 39′ of the sole plate 2 of the extension screed A. The rear lower end edge of the sole plate 2 is shown in
A lateral inclination measuring device 42 (e.g. an angle sensor, e.g. in the frame A2) and/or a height measuring device (not shown) for detecting the relative height difference between the rear lower end edge 2A of the sole plate 2 of the extension screed A and the rear lower end edge 1E of the sole plate 1 of the base screed G and/or a linear travel measuring device at or within the actuator 22 may be provided in the paving screed E or in the extension screed A (
In the embodiment of the paving screed E in
If in
While laying a paving mat 43 with a slope 44 it is necessary to counter a drift from the point of intersection 19 with respect to the base screed G as rapidly as possible when the working width is varied. In the road paver RF (or in a not shown exterior control panel at the paving screed E) e.g. an actuation device with switches or buttons for actuating the control device C is provided. The buttons or switches may be manipulated one by one by the operator of the road paver or by personnel. The switch or button for controlling the actuator 22 could be blocked selectively. When releasing the function of this switch or button from a blocked condition the button or switch for controlling the adjustment assemblies 3 is coupled with the switch or button for retracting or extending the extension screed A such that when actuating the switch or button for extending or retracting the extension screed A the necessary height adaptation is executed automatically. With a given linear speed of the adjustment assemblies 3, expediently, the speed of the extension or retraction of the extension screed A should become correlated with the speed of the height adaptation such that the point of intersection 19 is held stationary. In other words, the respective lateral position of the point of intersection 19 first may be set for later regulating operations in the control device C. For such regulating operations also others method could be used, e.g. even a fully automatic regulating method.
The extension screed A in
The further embodiment of the paving screed E shown in
Both extension screeds A are maximally extended in
A drive 20 which is common for both adjustment assemblies 3, 30, 31 of each extension screed A is mounted at the extension guiding structure A1. The drive 20 is in driving connection with the screw spindles of the adjustment assemblies 3, 30, 31 via chain drives or transmission trains 36.
The further structure of the paving screed E in
The edger plate 48 is mounted at the mounting plate 46 in
In
The embodiment in
The lateral position of the transition or point of intersection 19, 19′ is held stationary with respect to the base screed G, if the working width is varied, by actuating the adjustment assemblies 3, 30, 31 matched with the retraction or extension (drive 14, 12). The intermediate frame 61 is lifted while the extension screed A is retracted. The intermediate frame 61 is lowered while the extension screed A is extended.
Number | Date | Country | Kind |
---|---|---|---|
08021844.9 | Dec 2008 | EP | regional |