Step element for a system for conveying people, and pressure die-casting tool for a step element
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-05-13
- Publication Date
- 2026-04-08
AI Technical Summary
Existing tread elements for passenger transport systems, such as escalators and moving walkways, face challenges in optimizing wall thickness due to local segregation of alloy components during the die-casting process, leading to uneven mechanical properties and material inefficiencies.
Incorporating a rib structure on the tread surface and a wave structure on the rear side with a turbulence structure in the die-casting tool to generate a turbulent flow, preventing segregation of alloy components and allowing for reduced wall thickness while maintaining uniform mechanical properties.
The solution enables the production of weight-optimized tread elements with improved mechanical properties and reduced material usage, while also accelerating the solidification process and shortening production cycles.
Smart Images
Figure EP2024063084_28112024_PF_FP_ABST
Abstract
Description
[0001] Tread element for a passenger transport system and die-casting tool for a tread element
[0002] Description
[0003] The present invention relates to a tread element for a passenger transport system which is designed as an escalator or moving walkway and to a die-casting tool for producing such a tread element.
[0004] A passenger transport system designed as an escalator or moving walkway can have a circumferentially arranged step band made up of tread elements arranged one behind the other and connected to one another in an articulated manner, which are arranged close together at least on an upper side of the passenger transport system and form a walkable tread surface of the passenger transport system.
[0005] The tread elements can be made of die-cast metal (particularly aluminum die-cast products made of light metal alloys whose main alloying component is aluminum) and manufactured in a die-casting tool (mold). To require as little metal material as possible, the wall thicknesses of the tread elements can be optimized. However, during the production of tread elements, it has been shown that narrow channels in the die-casting tool strongly direct the flow of the liquid metal within a die-casting tool, causing alloy components to separate from the melt and settle locally in undesirable concentrations. These concentrations can lead to local weakening in the solidified tread element, thus limiting the reduction or optimization of wall thicknesses.
[0006] For example, WO 2009 / 010495 A2 describes a step element for a transportation system. Furthermore, WO 2019 / 048306 A1 describes a step unit for a passenger transportation system and a method for manufacturing a step unit.
[0007] There may be a need, among other things, for a weight-optimized, improved tread element for a passenger transport system, as well as an improved die-casting tool for producing such an improved tread element, in particular with a desired distribution of alloy components.
[0008] Such a need can be met by an improved step element for a passenger conveyor system, as well as an improved die-casting tool for producing such a step element, according to the main claims. Advantageous embodiments are defined in the dependent claims and described in the description.
[0009] According to a first aspect of the invention, a tread element made of die-cast metal for a passenger transport system is proposed, wherein the tread element has a rib structure on a tread surface and a wave structure on a rear side of the tread surface, wherein a wave trough of the wave structure is arranged opposite a tread rib of the rib structure, in particular in order to save metal material in the region of a rib base of the tread rib. An impression of a turbulence structure formed in a die-casting tool for the tread element for generating a turbulent flow during casting of the tread element is arranged on at least a partial region of the wave structure, wherein the impression protrudes from the wave structure and, following a contour of the wave structure, depicts the wave trough structure.The turbulence structure prevents the flow of the liquid metal within a die casting tool from becoming strongly directed, which would otherwise result in the alloy being separated (in particular the distribution of metal oxides within the molten metal).
[0010] As previously described, the imprint of the turbulence structure protrudes from the surface with the wave structure, but the imprint height of this imprint is less than the level differences of the wave structure, so that the imprint essentially follows the wave structure. As a result, the wave troughs are not stiffened by the imprint, and the elastic behavior of the tread surface with the turbulence structure essentially corresponds to the elastic behavior of a tread surface of the same size without the turbulence structure.
[0011] According to a second aspect of the invention, a die-casting tool for a tread element of a passenger transport system is proposed, wherein a negative of a rib structure of a tread surface of the tread element is formed in a mold cavity of the die-casting tool and, opposite thereto in the mold cavity, a negative of a wave structure of a rear side of the tread surface corresponding to the rib structure is formed, wherein a negative of a wave trough of the wave structure is arranged opposite a negative of a tread rib of the rib structure, in particular in order to save material in the region of a rib base of the tread rib. A turbulence structure for generating a turbulent flow during casting of the tread element is arranged at least on a partial region of the negative of the wave structure. The turbulence structure consists of recesses in the die-casting tool and wherein the recesses, following a contour of the negative of the wave structure, reproduce the wave structure.
[0012] In the following, a basic idea for embodiments of the invention described herein will be explained in more detail, whereby this explanation is to be interpreted as merely a rough summary and not as limiting the invention:
[0013] An aluminum alloy generally comprises various alloying constituents. The alloying constituents influence the mechanical properties of a casting made from the aluminum alloy. For example, the tensile strength of the aluminum alloy can be significantly higher than the tensile strength of pure aluminum. Important alloying constituents can be oxides, particularly aluminum oxides. The oxides can adhere to a surface of the casting and form an oxide skin. Likewise, certain alloying constituents can strain the metal lattice of the solidified aluminum alloy. Due to the oxide skin and / or the strain on the metal lattice, the casting can exhibit high flexural rigidity.
[0014] During casting, a mold cavity is filled with molten metal from a sprue. Any air contained in the mold cavity is displaced by the liquid melt. In die casting, the melt is "shot" at high speed and high pressure into the mold cavity of a metal die-casting tool or into a permanent mold. Despite the high speed, a directed laminar flow can develop in the melt, particularly along linear contours of the mold cavity. Due to the laminar flow, the concentrations of alloying constituents in the melt can locally increase or decrease. For example, a locally increased oxide concentration can make the casting so hard during solidification that it becomes brittle. A locally decreased concentration of an alloying constituent can, for example, make the casting so soft during solidification that it undergoes plastic deformation under load.
[0015] Linear structures can be created, in particular, by ribs and / or grooves in the mold cavity. If the melt flows along the ribs and / or grooves while filling the mold cavity, the usually turbulent flow at the sprue can transform into laminar flow. Such linear structures can be present, for example, where efforts are made to keep the wall thickness of the casting as constant or as small as possible. In this case, for example, ribs on one side of the casting can be compensated for by recesses on an opposite side of the casting to prevent material accumulation at the base of the rib. Such a design can save considerable amounts of material per casting.
[0016] The approach presented here achieves mixing of the alloy constituents of the melt even in the area of such linear structures. The flow of the melt is deliberately disrupted at least in some areas during the casting process. For this purpose, a turbulent structure in the form of recesses in the linear structures is superimposed on the linear structures of the casting mold. Turbulence is generated in the flow at these recesses, preventing the formation of laminar flow or generating turbulent flow again. The recesses can be essentially sharp-edged in order to create local turbulence at the edges of the recesses. The recesses are filled by the melt during casting and form elevations on the casting. These elevations on the casting are thus an imprint of the turbulent structure.
[0017] The impression or its elevations on the casting have no mechanical function, i.e., they do not influence the mechanical properties of the casting, or at least do not significantly influence them. The elevations are particularly small compared to the wall thickness of the casting. For example, the impression height of the elevations can be less than 50%, less than 30%, or even less than 15% of the wall thickness, with the wall thickness being understood as the average value of the wall thickness of the casting over its entire extent or, alternatively, as the wall thickness in an area of the casting directly adjacent to the elevation.
[0018] To achieve a consistently low imprint height of the elevations and to avoid stress peaks in the elevations, the contour of the elevations or imprint is adapted to the contour of the linear structures. The elevations thus follow the contour of the linear structures. Accordingly, the average imprint height of the imprint can be between 5% and 50% of the trough height of the wave trough. Preferably, the imprint height is between 20% and 40%, or more preferably, between 25% and 35% of the trough height.
[0019] The approach presented here makes it possible to avoid undesirable local concentrations of alloy components in, on and / or downstream of areas where laminar flow would conventionally develop during casting. By maintaining the desired mixing ratios or desired alloy composition, the mechanical properties of the casting can be specifically influenced. By reliably achieving the mechanical properties, the casting can be cast with reduced wall thicknesses and still exhibit high fatigue strength. The reduced wall thicknesses allow the casting to be lightweight. Furthermore, the additional recesses can provide an increased surface area between the die casting tool and the melt, resulting in improved heat transfer from the melt to the die casting tool.This accelerates the solidification of the casting and shortens the production cycle time. By preserving the underlying linear structures even at the superimposed turbulence structure, mechanical stiffening of the casting can be avoided.
[0020] In the following, possible designs and advantages of embodiments of the tread elements or the die-casting tool are described in more detail.
[0021] Tread elements of the aforementioned type are used in passenger transport systems designed as escalators or moving walkways. The passenger transport system has a circumferentially movable step belt made up of tread elements arranged one behind the other and connected to one another by an articulated connection. In an area of the passenger transport system accessible to users, the step belt has a movable usable surface which can be relocated circumferentially between opposite access areas. A tread element can be a step of the escalator or a pallet of the moving walkway. A tread surface of the tread element is provided on the upper side of a tread element. The usable surface is composed of the tread surfaces of several tread elements. In a moving walkway, the tread surfaces can form an essentially flat surface without any significant height offset.In an escalator, the treads may be offset in height from one another in a sloped section. A step of an escalator may have an arched front rail aligned perpendicular to the tread.
[0022] A ribbed structure consisting of tread ribs is arranged on the tread surface, i.e., on the upper side of the tread element. The tread ribs are aligned in the transport direction of the passenger transport system so that they can mesh with the fixed comb structures of a comb plate located at the access points of the passenger transport system. The meshing of the rib structures can prevent objects from being drawn into a gap between the tread surface and the comb plate at the end of the passenger transport system. The tread ribs can be tapered due to a raised section, i.e., they become thicker towards the base of the rib.
[0023] On the back of the tread surface, i.e. on the underside of the tread element, a wave structure consisting of adjacent wave troughs and intermediate wave crests is arranged. The wave troughs are also aligned in the transport direction and run parallel to the tread ribs. The wave troughs on the back can be arranged exactly below the tread ribs on the tread surface. In other words, the wave troughs can be arranged opposite the tread ribs of the rib structure. Each tread rib can be assigned a wave trough, and the wave trough can run at the shortest possible distance from the assigned tread rib. The wave troughs prevent material from accumulating at the base of the rib below the tread ribs. Providing the wave troughs can therefore save material.In particular, the provision of the wave troughs can contribute to a material thickness remaining largely the same at different points along the tread element, i.e., for example, varying by less than 50%, preferably less than 30% or less than 10%.
[0024] The tread element can be formed as a die-cast component by pressure casting in a permanent mold or a die-casting tool. The permanent mold can be filled with melt from one side to the other to avoid air pockets. During filling, the melt flows rapidly along the contour of a mold cavity. Since the rib structure and the wave structure are essentially linear structures and influence the flow direction of the melt during casting, the melt can transition to laminar flow at these linear structures.
[0025] In the approach presented here, a turbulence structure is incorporated into at least some areas of the linear structures, especially the wave structure, to prevent transition to laminar flow. The turbulence structure can consist, for example, of sharp-edged recesses in the contour of the mold.
[0026] As the fluid flows past the turbulent structure, eddies or turbulences are generated in the melt at the edges of the turbulent structure. These eddies cause a transition from a laminar flow to a turbulent flow. Compared to laminar flow, turbulent flow reduces the boundary layer at the contour and achieves a more uniform velocity distribution in the melt. At least one of these effects leads to increased mixing of the melt compared to laminar flow and thus to a more uniform distribution of alloy components in the melt.
[0027] The turbulence structure in the die-casting tool can have a depth that is small compared to the structures intended to form the rib structure and / or the wave troughs, in particular less than 50%, less than 40%, or even less than 10% of their depth. Accordingly, the impression created on the back of the tread element during casting due to the turbulence structure embedded in the die-casting tool can have a small impression height compared to the height dimensions of the rib structure and / or the wave trough height of the wave structure. Due to this small impression height, the impression does not affect the mechanical properties of the tread element, or at most only insignificantly.
[0028] The turbulence structure can have a substantially constant depth, since the swirling effect does not increase with depth. In other words, the recesses in the die-casting tool which form the turbulence structure represent, or at least substantially represent, a contour of the negative of the wave structure. In other words, a depth by which the turbulence structure protrudes from a surface of the mold cavity into the die-casting tool can be substantially constant in all regions of the mold cavity, in particular also along the depressions of the negative of the wave structure. This accordingly causes the resulting impression to protrude from the wave structure and substantially represent a contour of the wave structure, or in other words, to protrude substantially as high above the surface in deeper regions of the wave structure as in higher regions thereof or in regions between adjacent wave troughs.
[0029] Due to the essentially uniform depth of the turbulence structure, any influence on the mechanical properties of the tread element, for example, due to stiffening caused by the turbulence structure's imprints, can be minimized. In particular, this prevents mechanical overloading of the imprints when the tread element bends.
[0030] The turbulence structure can also be arranged on the back of the front cheek.
[0031] The turbulence structure can, for example, have similar dents as recesses in the contour of the wave structure, which are evenly distributed over the surface. The recesses can also be elongated. The recesses can be offset from one another. In particular, edges of the turbulence structure oriented transversely to a flow direction can be essentially sharp-edged, wherein the flow direction refers to a melt flowing through the mold cavity of the die-casting tool during casting of the tread element. The impression of the turbulence structure generally has a shape complementary to the turbulence structure and accordingly protrudes above a surrounding surface of the tread element. The impression of the turbulence structure can consist of fine ribs that protrude from the wave structure. The fine ribs can be narrow and low.The fine ribs can be essentially sharp-edged or have only broken edges. In particular, a minimum radius of curvature at protruding edges of the impression or the fine ribs can be considerably smaller than minimum radii of curvature, for example, at the rib structure and / or the wave structure.
[0032] Recesses for the turbulence structure, or especially for the fine ribs, can be integrated into the mold contour with minimal manufacturing effort. For example, the recesses can be milled into the contour using a program-controlled process. The fine ribs can be designed, at least in partial areas, with the imprint of the turbulence structure, continuously and following the wave structure.
[0033] The fine ribs can be oriented in different directions. In particular, a first group of fine ribs can run in a first direction along the back of the tread element, and a second group of fine ribs can run in a second direction along the back of the tread element. The first direction and the second direction can be oriented transversely to each other.
[0034] The fine ribs can be connected to each other at nodes. Pockets enclosed by the fine ribs can be arranged between the fine ribs. The pockets can be arranged regularly on the back. The pockets can have simple geometric shapes. For example, the pockets can be diamond-shaped, square, honeycomb-shaped, or triangular. Alternatively, the fine ribs can also be interrupted. This avoids nodes and, consequently, material accumulation at the nodes.
[0035] The fine ribs can be oriented in only two different directions, i.e., a first group of fine ribs can run in a first direction, and a second group of fine ribs can run in a second direction. In this case, the pockets can be rectangular. The pockets can be distributed in a waffle pattern across the sections. Recesses for fine ribs in only two directions can be quickly and cost-effectively introduced into the mold.
[0036] The nodes can be arranged at regular intervals. The distances between the nodes can be different from the distances between the wave troughs. The nodes can be distributed irregularly throughout the wave structure. The turbulence structure can therefore have a different pitch / grid than the wave structure. In this case, the nodes at different wave troughs can have different relative positions to the wave troughs. By using different pitches / grids, harmonic oscillations caused by the turbulence can be avoided. Alternatively, the turbulence structure can have the same pitch / grid as the wave structure. In this case, the nodes of the fine ribs can be arranged at the same relative positions to the wave troughs.
[0037] The recesses for the fine ribs can be oriented at an angle transverse to the flow direction during casting or transverse to the wave troughs. In particular, the recesses can be oriented at an angle of more than 45° to the flow direction or the wave troughs. Inclining the recesses achieves an increased mixing effect of the melt.
[0038] The imprint height of the fine ribs above the contour of the wave structure can be approximately constant. The fine ribs are adapted to the contour of the wave structure or follow the contour of the wave structure. The fine ribs have a raised area if the contour of the wave structure has a raised area. The fine ribs have a recessed area if the contour of the wave structure has a recessed area. A constant imprint height can prevent bending stress peaks at higher points of the fine ribs.
[0039] The fine ribs on the tread element or the recesses for the fine ribs in the die-casting tool or in the mold can have a triangular cross-sectional area, at least outside the wave troughs. The fine ribs can therefore have a sharp-edged rear side. Recesses with a triangular cross-sectional area can have a small volume and only insignificantly increase the total volume of the mold cavity.
[0040] The imprint of the turbulence structure can be interrupted by at least one smooth ejector surface. The wave structure can also be interrupted by the ejector surface. An ejector of the mold can rest against the casting at the ejector surface. To remove the casting from the mold, the mold can be opened. Slides of the mold can be retracted and the ejectors can extend, press against the casting and push the casting out of the contour of the mold. The ejectors can be round or circular and require corresponding ejector surfaces on the casting. The ejector surfaces can be large to avoid deformation of the casting during ejection. With circular ejector surfaces, the turbulence structure can continue in the inner circle.By interrupting the wave structure in the area of the ejector surface, the casting can have increased rigidity there in order to avoid deformation during ejection.
[0041] The tread element can also have impressions of turbulence structures on at least partial areas of the side cheeks of the tread element to create a turbulent flow during casting. The impressions on the side cheeks can have a different or the same pitch as the impressions on the wave structure. The impressions of the turbulence structure on the side cheeks can be arranged on an outer side of the side cheeks. An inner side of the side cheeks can be smooth. The impressions can be formed onto the side cheeks by a turbulence structure on lateral slides of the mold. The slides are retracted to eject the tread element and thereby release undercuts on the side cheeks. The mold can be designed without slides on the inner side.
[0042] It should be noted that some of the possible features and advantages of the invention are described herein with reference to different embodiments of methods, on the one hand, and devices, on the other. A person skilled in the art will recognize that the features can be combined, adapted, or exchanged as appropriate to achieve further embodiments of the invention. Embodiments of the invention are described below with reference to the accompanying drawings, whereby neither the drawings nor the description should be construed as limiting the invention.
[0043] Fig. 1 shows a representation of a tread element according to an embodiment; and
[0044] Fig. 2 shows a representation of a turbulence structure on a back side of a tread element according to an embodiment.
[0045] The figures are merely schematic and not to scale. Like reference numerals denote like or equivalent features.
[0046] Fig. 1 shows a representation of a tread element 100 for a passenger transport system. The passenger transport system can be an escalator or a moving walkway. The tread element 100 is a step of an escalator, but can also be, for example, a pallet of a moving walkway. The tread element 100 is a die-cast part. The tread element 100 has a tread surface 102 on its upper side. Passengers can stand with their feet on the tread surface 102.
[0047] On an upper side of the tread surface 102, the tread element 100 has a rib structure 104 composed of tread ribs. On a rear side 106 of the tread surface 102, the tread element 100 has a wave structure 108 composed of wave troughs 202 (see also Figure 2), corresponding to the rib structure 104. The tread ribs and the wave troughs 202 are aligned with one another and arranged exactly opposite one another on the tread surface 102 and the rear side 106. The wave structure 108 prevents material from accumulating at the rib bases of the tread ribs. As a result, the tread surface 102 has a more uniform wall thickness than without the wave structure 108.
[0048] In partial areas 110, the wave structure 108 is overlaid by impressions 112 of a turbulence structure for generating turbulence during casting. The turbulence structure is an auxiliary structure for the production of the tread element 100 by a die-casting process. During production, a molten metal alloy or a melt, in particular of an aluminum alloy, is introduced into a die-casting tool and solidifies in a mold cavity of the die-casting tool. The die-casting tool is made of metal and can be referred to as a permanent mold. The melt fills the mold cavity starting from a sprue of the permanent mold, thereby forming a contour of the mold cavity. The melt then cools in the mold cavity and solidifies to form the die-cast part. The solidified die-cast part then has an inverse contour of the mold cavity. The mold cavity thus forms a negative mold of the die-cast part.
[0049] A surface of the mold cavity is essentially smooth or has a slight roughness. On the smooth surface and particularly on linear structures of the mold cavity, such as the rib structure 104 and the wave structure 108, the melt can transition to a laminar flow when filling the mold cavity. Due to the laminar flow, alloy constituents of the melt can be distributed unevenly or local
[0050] Concentration differences in the alloy components can develop. This can be undesirable.
[0051] The turbulence structure improves the mixing of the alloy components of the melt during filling of the mold cavity by causing or restoring a turbulent flow at least in the region of the partial regions 110. The impressions 112 of the turbulence structure on the tread element 100 are created by molding the turbulence structure of the die-casting tool.
[0052] In one embodiment, the impressions 112 of the turbulence structure extend from a front edge of the tread element 100 to a main stiffening rib 114 on the rear side 106. Due to the turbulence structure, the melt enters a cavity of the die-casting tool for the main stiffening rib 114 in a highly mixed state. This prevents local concentrations of individual alloy constituents in the melt. In particular, locally elevated concentrations of oxides in the region of the main stiffening rib 114 can be avoided. These locally elevated concentrations would locally increase the stiffness of the main stiffening rib 114 and locally embrittle the main stiffening rib 114. Due to the thorough mixing due to the turbulence structure, a largely homogeneous mixing of the alloy constituents can be achieved in the main stiffening rib 114.The main stiffening rib 114 can therefore be designed with a thin wall thickness of, for example, 1.4 millimeters, since the main stiffening rib 114 can be designed with reduced load reserves. In other words, the turbulence structure not only directly affects the surfaces covered with the indentations 112, but also, in particular, adjacent areas of the tread element 100, such as the main stiffening rib 114, which has no indentations.
[0053] In one embodiment, the tread element 100 has four separate subregions 110 with impressions 112 of the turbulence structure. The subregions 110 are arranged spaced apart from one another between the leading edge and the main stiffening rib 114.
[0054] In one exemplary embodiment, ejector surfaces 116 for ejectors of the die-casting tool are arranged in at least one partial region 110. The ejector surfaces 116 are large-area circular rings without a wave structure 108 and without impressions 112 of the turbulence structure. The wave structure 108 and the impressions 112 of the turbulence structure continue in inner circles of the ejector surfaces 116. The turbulent flow does not transform into a laminar flow in the region of the ejector surfaces 116. The ejector surfaces 116 therefore essentially do not reduce mixing when filling the mold cavity. In addition, the ejector surfaces 116 are surrounded on all sides by the impressions 112 of the turbulence structure, so that the melt flowing on from the regions of the ejector surfaces 116 is swirled again.
[0055] In one embodiment, additional impressions 112 of turbulence structures of the die-casting tool are arranged at least on partial areas 110 of side surfaces 118 of side cheeks 120 of the tread element 100. The turbulence structures also improve the mixing of the melt during casting on the side cheeks 120 and prevent undesirable concentrations of certain alloy components.
[0056] Fig. 2 shows an illustration of impressions 112 of a turbulence structure on the wave structure 108 of a tread element 100 according to an exemplary embodiment. The tread element 100 essentially corresponds to the tread element in Fig. 1. Here, a partial section of a partial area 110 is shown in detail. The impressions 112 consist of low, fine ribs 200 that protrude from the wave structure 108. The fine ribs 200 are arranged approximately 45° transversely to the wave troughs 202 of the wave structure 108 or a flow direction when filling the mold cavity. The fine ribs 200 are formed in the mold cavity as grooves in the contour of the mold cavity. At the edges of the grooves, turbulence is caused in the melt at each groove. The melt is thereby set into a turbulent flow and intensively mixed.The grooves or the fine ribs 200 are low compared to other stiffening components of the contour and do not fulfill any essential mechanical function on the tread element 100.
[0057] In order to consistently achieve a low imprint height of the fine ribs 200 or elevations and to avoid stress peaks in the ribs 200, a contour of the fine ribs 200 is adapted to a contour of the wave structure 108. The fine ribs 200 thus follow the contour of the wave structure 108. Accordingly, an average imprint height HA of the impressions 112 is between 5% and 50% of a wave trough height HW of the wave trough 202. Preferably, the imprint height HA of the impression 112 is between 20 and 40% or particularly preferably between 25 and 35% of the wave trough height HW.
[0058] In one embodiment, the impressions 112 consist of groups of fine ribs 200 crossing in two opposite directions. The fine ribs 200 are connected to each other at nodes 204.
[0059] In one embodiment, the fine ribs 200 are evenly spaced. The spacing is selected such that the nodes 204 are arranged in different relative positions to the wave troughs 202 of the wave structure 108.
[0060] In one exemplary embodiment, an upper edge of the fine ribs 200 or a rib head of the fine ribs 200 precisely follows the contour of the underlying wave structure 108. As a result, the fine ribs 200 are always the same height and also have depressions in the area of the wave troughs 202. This reduces mechanical stress on the fine ribs 200 in the area of the wave troughs 202 when the tread element 100 bends. Possible embodiments of the invention are summarized again below or presented using slightly different terminology.
[0061] A step with a waffle-like rib structure on the underside of the step tread is presented.
[0062] This waffle-like rib structure is advantageous in optimizing a wave structure of grooves on the underside of the step in the area of the tread webs to reduce weight below the tread. Without a waffle-like rib structure, local aluminum oxide concentrations could occur, especially in the central region of the large stiffening rib, which would lead to a structural weakening of the aluminum die-cast step. The waffle-like rib structure therefore primarily serves to swirl the melt during the die-casting process. The fine ribs of the waffle-like rib structure are aligned with the surface of the wave structure. This prevents cracks from forming at the rib tips by adapting to the wave structure. The fine ribs aligned with the step structure result in consistently high elasticity and prevent stress concentrations.Under load, high bending stress concentrations could occur in the outermost fibers of the fine ribs in the area of the wave troughs 202 due to the bending if the ribs are straight. Furthermore, the fine ribs, which are positioned in a straight line, save some material, which significantly reduces material costs for high-volume applications.
[0063] The waffle-like rib structure can be arranged across the entire underside. The waffle-like rib structure can also be arranged only partially on the underside. The surface with the wave structure and the rib structures can have flat areas. The flat areas can, for example, be annular surfaces for ejectors. Due to their limited size, the flat areas hardly affect the turbulent flow.
[0064] A waffle-like rib structure can also be arranged on the side surfaces of the side cheeks. The right and / or left edge area can be designed with a recess. The tread element can be designed as a single-piece aluminum die-cast part. Alternatively, the tread element can be made of multiple pieces. Finally, it should be noted that terms such as "having," "comprising," etc. do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a plurality. Furthermore, it should be noted that features or steps described with reference to one of the above exemplary embodiments can also be used in combination with other features or steps of other exemplary embodiments described above. Reference symbols in the claims are not to be considered as limitations.
Claims
Patent claims 1. Tread element (100) for a passenger transport system, wherein the tread element (100) has a rib structure (104) on a tread surface (102) made of die-cast metal and a wave structure (108) on one of the rear sides (106) of the tread surface (102), wherein a wave trough (202) of the wave structure (108) is arranged opposite a tread rib of the rib structure (104), wherein an impression (112) of a turbulence structure formed in a die-casting tool for the tread element (100) for generating a turbulent flow during casting of the tread element (100) is arranged on at least one partial area (110) of the wave structure (108), wherein the impression (112) protrudes from the wave structure (108) and, following a contour of the wave structure (108), depicts the wave structure (108).
2. Tread element (100) according to claim 1, wherein an average imprint height (HA) of the imprint (112) is between 5 and 50%; preferably between 20 and 40%; particularly preferably between 25 and 35% of a trough height (HW) of the trough (202).
3. Tread element (100) according to claim 1 or 2, wherein the imprint (112) consists of continuous, fine ribs (200).
4. Tread element (100) according to claim 3, wherein the fine ribs (200) are aligned in different directions and are connected to one another at nodes (204), wherein pockets enclosed by the fine ribs (200) are arranged between the fine ribs (200).
5. Tread element (100) according to claim 4, wherein the nodes (204) are arranged at regular intervals, wherein distances between the nodes (204) are different from distances between the wave troughs (202).
6. Tread element (100) according to one of claims 3 to 5, wherein the fine ribs (200) are aligned at a transverse angle to the wave troughs (202).
7. Tread element (100) according to one of claims 3 to 6, wherein an imprint height (HA) of the fine ribs (200) over the contour of the wave structure (108) is approximately constant.
8. Tread element (100) according to one of claims 3 to 7, wherein the fine ribs (200) have a triangular cross-sectional area at least outside the wave troughs (202).
9. Tread element (100) according to one of the preceding claims, wherein the impression (112) is interrupted by at least one ejector surface (116).
10. Tread element (100) according to one of the preceding claims, wherein the tread element (100) also has impressions (112) of turbulence structures of the die-casting tool at least on partial areas (110) of side walls (120) of the tread element (100).
11. A die-casting tool for a tread element of a passenger transport system, wherein a negative of a rib structure (104) of a tread surface (102) of the tread element (100) is formed in a mold cavity of the die-casting tool and, opposite thereto in the mold cavity, a negative of a wave structure (108) of a rear side (106) of the tread surface (102) corresponding to the rib structure (104), wherein a negative of a wave trough (202) of the wave structure (108) is arranged opposite a negative of a tread rib of the rib structure (104), wherein at least on a partial area (110) of the negative of the wave structure (108) a turbulence structure for generating a turbulent flow during the casting of the tread element (100) is arranged, wherein the turbulence structure consists of recesses in the die-casting tool, wherein the recesses follow a contour of the negative of the wave structure (108), the wave structure depict.