EP1431460B1 - Roadpaver and heating unit - Google Patents

Description

The invention relates to a road paver specified in the preamble of claim 1 and a type of heating element according to the preamble of claim. 8

When working with a hot paving material paver working components must be heated until the built-in material is no longer prone to sticking. The temperature of the paving material is about 170 ° C. It is usually heated before the start of installation and reheated during installation. The working components may be the screed plates in the screed, the tamper bars, pressure bars or paving material containers. In practice, it is customary to mount on the heating area of the screed plate at least one electric Flachheizstab which is supplied by a three-phase alternator of the paver with three-phase current. Also in the Tamperleiste or optionally provided pressure bar at least one electrical Flachheizstab is introduced. The well-known Flachheizstab consists for example of a drawn round tube, which is pressed flat, so that flat top and bottom sides arise. In the flat tube, a heating coil of a helical spring-wound heating wire is inserted serpentine and secured by a Keramikpulverschüttung insulating and positioned. Such Flachheizstäbe can be produced only with a width just below 20 mm. Due to the design, effective heat transfer takes place essentially only in the middle region of the already narrow support surface, whereas in the edge regions of the support surface it is hardly heated. This results in an unfavorable heating pattern in the heating area of the working component. Furthermore, there are long heating times and uneven heating patterns. Another disadvantage is that the heating elements are formed with an integrated, slim connector housing at one end of the rod, which rises vertically from the heating element and easily damaged by the aggressive media used in the paver. When exchanging a flat heating element, always replace the connection housing together with the electrical connection cable. Due to the difficult heat transfer of Flachheizstabes a relatively high electrical supply power is needed. Usually in one Paver a plurality of such heating elements is installed, this means an undesirable high load on the alternator.

The flat heating element is conventionally clamped onto the screed plate with clamping screws that are upstanding from the screed plate and an overlying metal profile. The clamping screws must be arranged laterally next to the heating element. Direct heating of the alley defined by the clamping screws in the heating area is not possible.

At one off US-B-6,318,928 known road finisher are mounted on the screed plate screed several rod-shaped planar heating elements with acting from above clamping devices. In order to adapt to a desired heating pattern in the heating area, a heat distributing plate is either mounted under the flat heating elements or the flat heating elements are clamped in a denser arrangement and larger numbers directly on the screed plate. Each planar heating element is a hollow metal rod with an inner resistance coil. The flat heating elements have constant width over their length.

Out DE-C-460 333 For example, a planar electric heating element is known, which contains in a rigid metal shell a jacket of thin sheet metal, which surrounds an insulated heating coil. The heating coil is wound on a strip of asbestos over the length of the heating element of uniform winding density. The thickness and width of the strip are constant over the length of the heating element.

The invention has for its object to provide a paver of the type mentioned above or a heating element for a paver with which an optimized heating with a desired heat pattern in each heating is possible.

The stated object is achieved with the features of patent claim 1 or claim 8.

The flat heating element can be well adapted to the heating area in its width and length and a contour contour tailored to the desired heating pattern, resulting in effective heat transfer over the entire width of the heating element. The heating effect of the heating element can be variable over its length and width be. Variable means that in zones of the heating area where more heat is needed for a given heating pattern than in other zones, more heating is provided by the heating element per unit area. This can be achieved on the one hand by the outline of the wrapped with the heating element carrier material with constant winding density and / or by varying the winding density of the heating, wherein the carrier material substantially determines the shape and size of the heating element, and the heating element is adapted to the conditions on the substrate. The optimal heat pattern can be achieved with moderate power consumption of the heating element. Optionally, the heat is distributed to an even greater width and / or length with an intermediate member. The flat heating element is also suitable for tamper bars or pressure bars or containers to be heated.

The heating conductor should have band-shaped cross-section, so that it can be wrapped comfortably and tightly around the carrier material. For example, tungsten or a tungsten alloy may be used as the material for the heating conductor.

In order to temporarily or permanently increase the heating power as required and / or to optionally change the heating pattern, at least one second (or even further) heating conductor can be provided on the carrier material, which can be selectively activated. This may also be appropriate for redundancy, e.g. in case of failure of another heating conductor.

The heating element should be suitably wound around the carrier material so that the turns remain spaced from each other. The winding density can be constant over the length of the carrier material, so that the heating element provides approximately the same heat output per unit area. In applications where the heating zone has zones of increased heat demand for a particular heating image, for example, because heat-absorbing devices or masses are located nearby, the winding density can be variable, ie, in zones of increased heat demand, the heating power per unit area is greater than in other areas of the heating element. Optionally, at least one further optionally activatable heating conductor is provided in a zone with increased heat demand.

In order to increase the efficiency in the heating of the heating area, an insulating layer may be provided on the side facing away from the heating area of the wound with the heating element carrier material. The insulation layer drives the heat in the desired direction in the heating area, so to speak. The insulating layer can be integrated in the heating element and / or mounted on an outer side of the heating element.

In view of the rough working conditions in the paver, the carrier material wrapped with the heating element should be enclosed between flat cover plates, sealed in such a way that no aggressive media can penetrate. The lower cover plate may form a heat-distributing intermediate member. Alternatively, a heat-distributing intermediate member may be placed under the lower shroud.

Structurally simple, the cover plates are sealed together in the edge region of the heating element. For example, the edge of the one, larger sized cover sheet is wrapped around the edge of the other cover sheet, and optionally soldered or welded or otherwise sealed. The material for the cover plates is steel or aluminum. The planar heating element may have a total thickness of only between 4.0 and 10.0 mm, suitably only about 5 to 6 mm, wherein carrier material needs to have a substantially uniform thickness between only 1.0 and 3.0 mm.

For a conventional size screed plate is a flat heating element with a length between 0.9 and 1.2 m, preferably of about 1.1 m, and a width of about 50 to 100 mm, preferably about 60 mm, wherein the heating element is designed for a power consumption between 500 and 1000 watts, preferably of only about 600 watts.

The carrier material is at least one strip. However, it is quite conceivable to place a plurality of strips of the carrier material next to each other, and to wrap each strip with the or a heating conductor, so that the ends of the heating element are led out on the same side of the heating element. In the heating element breakthroughs are provided for fasteners with which the heating element is mounted in a conventional manner on the screed plate. The breakthroughs can be easily passed through the heating element. This improves the fit of the heating element under operational conditions thermal stress and vibration forces, and also the defined by the clamping screws lane is heated in the heating of the Glättbleches.

With regard to ease of maintenance and operational safety, it is expedient to provide a connection box on the heating element, and expediently on the side facing away from the heating area. The connection box can be mounted via spacer elements or directly on the cover plate of the heating element. If necessary, a terminal block is provided in the connection box to connect the ends of the heating conductor and a connection cable and to be able to disconnect the connection during maintenance or replacement. The connecting cable can be inserted through a lateral passage in the terminal box, so that detergent or other aggressive liquids do not stop there, but run off immediately. As connection cable feedthrough can serve a conventional, heat-resistant cable gland which is substantially horizontal in the position of use of the heating element on the working component. The bushings for the heating conductor ends and / or the openings should be sealed with potting compound, so that no aggressive media penetrate into the interior of the heating element.

Fig. 1

eine schematische Seitenansicht eines Straßenfertigers,

Fig. 2

eine Perspektivansicht eines Glättblechs mit darauf montiertem Heizelement,

Fig. 3

einen Querschnitt des Heizelements,

Fig. 4

eine Perspektivansicht des Heizelements,

Fig. 5

eine Perspektivansicht eines Details des Innenaufbaus des Heizelements,

Fig. 6

einen Abschnitt des verwendeten Heizleiters in perspektivischer Darstellung,

Fig. 7

eine Draufsicht auf einen Teil einer abgeänderten Ausführungsform, und

Fig. 8

eine Perspektivansicht einer weiteren Ausführungsform.

Reference to the drawings, embodiments of the subject invention will be explained. Show it:

Fig. 1

a schematic side view of a paver,

Fig. 2

a perspective view of a Glättblechs with mounted heating element,

Fig. 3

a cross section of the heating element,

Fig. 4

a perspective view of the heating element,

Fig. 5

a perspective view of a detail of the internal structure of the heating element,

Fig. 6

a section of the heat conductor used in perspective,

Fig. 7

a plan view of a part of a modified embodiment, and

Fig. 8

a perspective view of another embodiment.

A paver F in Fig. 1 has a chassis 108 with front wheels 105 and rear wheels 106. On the chassis, a Gutbunker 113 is disposed at the front end, behind which is a diesel engine with a three-phase generator 115 as the primary drive source 114. Between the Gutbunker 113 and the rear end of the chassis extends a longitudinal conveyor 109, is stored with the paving as a template 111 behind the paver on the ground. At the rear end of the chassis a transverse distribution device 110 is arranged, which homogenizes the template 111 and spreads laterally. On side rails 104, a screed 103 is towed, which rides on the template 111 and forms a ceiling layer 112. The screed 103 has lower side Glättbleche 101, which are electrically heated with flat heating elements H. Furthermore, a tamper T is indicated, which works with an oscillating tamper strip 102 the built-in. The Tamperleiste 102 may also be equipped with a heating element, not shown. In special embodiments of screeds 103 and pressure bars (not shown) may be provided, which are also heated with heating elements. It is also possible to heat containers of the paver F not shown with such heating elements. The heating elements H are powered by the generator 115, for example, with three-phase current.

This in Fig. 2 Shining plate 101 shown is a steel plate on which a flat heating element H with clamping screws 3 is mounted. The clamping screws 3 pass through openings 4 of the heating element H. The heating element H is formed as an approximately rectangular strip, for example with a length of about 1.1 m and a width of about 60 mm. Under the heating element H may be provided a heat-distributing intermediate member 1, for example a metal profile. On the heating element H is a metal profile shown in broken lines 2. This structure is stretched with the clamping screws 3 on the screed 101. On the heating element H, a terminal box 6 is mounted, in which a connecting cable 7 is inserted horizontally. Dashed further components of the screed are also indicated at 5, if necessary. Contact the screed plate 102 and may require that there is a higher heat output per unit area is used in the screed plate 101, as in other areas. The intermediate member 1 'could be significantly wider and / or longer than the heating element H.

The cross section of the planar heating element H in Fig. 3 is not to scale, but exaggerated for the sake of clarity. The total height of the heating element H is only between 5 and about 10 mm. To generate heat, at least one heating conductor L is spirally wound around a flat carrier material M. The carrier material M, for example, has the consistency of a cardboard plate and only a thickness of about 1.0 mm, has an outline shape, which is adapted to the desired heating area or the required heat or heating image of the working component to be heated. Insulating layers 8 can be provided above and below the carrier material. Furthermore, it is expedient to provide above a thermal insulation 9 to selectively drive the heat down to the heating area. This layer construction is covered by a lower cover plate 10 and an upper cover plate 11, wherein an edge 12 of the lower cover plate 10 is folded up around the edges of the upper cover plate 11 and secured thereto tightly. Dashed lines the terminal box 6 is indicated, which can be mounted with spacers 13 directly on the upper cover plate 11. A thermal insulation (not shown) could also be provided in the side areas. The lower cover plate 10 forms a heat-distributing intermediate member, so that it may be possible to dispense with the separate intermediate member 1 or 1 '.

In the perspective view of the flat heating element H in Fig. 4 It can be seen how the openings 4 pass through the heating element H at the positions of the clamping screws of the screed plate. However, the flat heating element H could also be formed without any breakthrough. The junction box 6 with its spacer elements 13 expediently has a removable cover 6 a and a horizontal passage 6 b for the connecting cable 7. Inside the junction box 6, a terminal block indicated by dashed lines 14 may be provided, at which the heating conductor ends introduced into the connection box 6 and the connection cable 7 are connected to one another. After removal of the cover 6a, the connecting cable 7 can only be solved when replacing the heating element H and then remain in place. If necessary. the heating conductor L is connected directly to the connecting cable 7. The terminal box 6 then serves to determine the Heizleiterenden and the connecting cable, for example, to keep pulling forces from the heating element L.

Fig. 5 shows that the heating element L runs in, for example, wound transversely around the carrier material M windings 15, between which intermediate spacings 16 are present. x indicates a higher turn density region, while y indicates a lower turn density region. The apertures 4 can extend, for example, through the carrier material between the windings 15. In the area X, the heating power per unit area is greater than in the area y. The heating conductor L could alternatively be wound in the longitudinal direction of the carrier material M around this. Alternatively, at least one further, preferably selectively activatable heating conductor can be wound in turns 15 'around the carrier material M, which, for example, enables a second heating stage.

The heating conductor L is according to Fig. 6 expedient a profiled heating wire with rectangular or oval band cross-section and a bandwidth b between 1.0 and 5.0 mm and a band thickness h between 0.1 and 0.5 mm. The heating conductor L is placed with its flat side on the carrier material M and bent transversely to the strip thickness h.

Fig. 7 indicates that the openings 4 can alternatively be defined by two adjacent strips of the carrier material M. Each strip or at least one strip has a peripheral cutout 17 as enclosure of the opening 4. The respective heating conductor L is wound around the cutout edge, so that the surroundings of the opening 4 are heated. The Heizleiterenden are indicated at 18.

As a rule, one strip (or two adjacent strips) of the carrier material M will suffice to produce a predetermined heating pattern in the heating area with the uniform or varying winding of the heating conductor or with more than one heating conductor. The heating power per unit area can be varied by the winding density, or by the geometric outline of the support material M, and / or by means of at least one further heating conductor. The carrier material M can be cut into a convenient shape to take into account the requirements in the heating already by its shape. A narrower area of the carrier material M with then shorter turns of the heating conductor provides a lower heating power than a wider area of the carrier material with longer turns. Since the heating conductor L is wound around the carrier material, the heating conductor adapts to any desired outline contour of the carrier material M.

In Fig. 8 is as a heating element H a conventional heating rod (with round or, as shown, squashed flat cross section) stretched on the intermediate member 1, which rests flat on the heating of the Glättblechs 101 and distributes the heat in width and / or length in the heating area. The intermediate member 1 is a metal profile (steel or light metal) or with a heat transfer medium, such as thermal oil, filled hollow body. About the upper metal section 2 and the clamping screws 3, the heating element is clamped to the intermediate member 1 and the intermediate member 1 on the screed plate 101.

Claims (8)

1. Road paver (F) , including a paving screed (!03) having at least one working component which can be heated by an electric heating element (H) e.g. a smoothing plate (101) of the paving screed (103),
   the electric heating element (H) secured in heat transferring condition in a heating area of the working component, the heating element being planar and containing at least one heating spiral characterised in that the heating spiral is at least one heating conductor (L) wound spirally around a planar carrier material (M), and that the peripheral contour of the carrier material (M) and/or the winding density or the course of the windings of the respective heating conductor (L) varies within the heating element (H) in adaptation to a predetermined heating picture in the heating area of the working component.
2. Road paver as in claim 1, characterised in that the heating conductor (L) has a band-shaped cross-section, is laid with a flat side on the carrier material (M) and is bent crosswise to the band-thickness.
3. Road paver as in claim 1, characterised in that within the heating element (H) at least one further heating conductor is wound in windings (15') around the carrier material (M), the further heating conductor adapted to be selectively connected to a power supply.
4. Road paver as in claim 1, characterised in that a damp course (9) is provided in the interior of the heating element (H) at least at the side of the carrier material (M) on which the heating conductor is wound and which the side remote from the heating area of the working component.
5. Road paver as in claim 1, characterised in that the carrier material (M) around which the heating conductor (L) is wound is enclosed between flat metallic cover sheets (10, 11) among which the lower cover sheet forms a heat distributing intermediate member or is abutting on a heat distributing intermediate member (1, 1'), and that the cover sheets (10, 11) being sealed and connected with each other in the edge region of the heating element (H), preferably, by folding the edge (12) of one cover sheet (12) around the edge of the other cover sheet (11).
6. Road paver as in claim 1, characterised in that the planar heating element (H) comprises breakouts (4) for accepting fastening elements of the working component, the breakouts (4) either penetrating the carrier material (M) between spaced apart windings (15, 15') of the heating conductor (L) or that two carrier material strips extending longitudinally are juxtaposed, at least one of the strips having a cut-out (17) in its edges as the boundary of the breakout (4), and that the heating conductor (L) being wound around the edge of the cut-out, in some cases only locally.
7. Road paver as in claim 5, characterised in that directly on the cover sheet (11) a connection box (6) is fixed to the side of the planar heating element (H) which is remote from the heating area, preferably via spacing elements (13).
8. Heating element (H), which is planar and contains at least one heating spiral for electrically heating a heating area of a working component of a road paver, in particular, a smoothing plate (101), a tamper bar or a pressing bar (102), characterised in that the heating spiral comprises a first and at least a second heating conductor (L) which selectively is to be supplied with current, that the heating conductors (L) spirally are wound in windings (15, 15') around a planar carrier material (M), and that the peripheral contour of the carrier material (M) and/or the winding density or the course of the windings of the heating conductors (L) is or are varied within the heating element (H) in adaptation to a predetermined heating picture in the heating area.

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