Belt bending and centring unit for z-shaped conveyor

Abstract

FIELD: conveyors.SUBSTANCE: Z-shaped conveyor belt bending and centring unit contains lateral bearing parts located on both sides of the belt and a system of rollers interacting with the belt in the transition zone, including holding, supporting and adjusting rollers. The lateral load-bearing parts are connected to each other by at least one integral connecting plate and at least one integral connecting element of the channel profile to form a rigid spatial structure that ensures mutual coaxiality of the lateral load-bearing parts. The connections of the unit elements are made to ensure a fixed mutual position of the said parts without excessive gaps and to exclude their mutual displacement relative to each other. The unit also contains corner rollers, which are located in the belt bending zone. At least some of the rollers are installed with the possibility of adjusting their position. The surfaces of the unit elements that interact with the tape in the bending zone are rounded.EFFECT: ensuring stable, centred movement of the belt in the bending zone, increasing the coaxiality of the unit elements, reducing the likelihood of the belt slipping and being damaged, and also increasing the reliability of the conveyor operation.13 cl, 1 dwg

Description

[0001] Technical field

[0002] The invention relates to transport equipment intended for moving bulk materials and can be used in belt conveyors, including conveyors with a belt transition between sections located at an angle to each other.

[0003] More specifically, the invention relates to conveyor belt bending and centering units that ensure its directed passage in the transition zone between sections of the conveyor, holding the belt in the working position, forming its smooth bend, as well as reducing belt slippage, distortion and damage during operation.

[0004] The invention can be used in equipment for transporting grain, seeds, compound feed, oilcake, granulated, construction and other materials, including various bulk materials for processing and production.

[0005] Technology Level

[0006] The prior art includes technical solutions aimed at guiding a conveyor belt through transition and curved sections, preventing it from drifting laterally, and reducing belt wear in areas where the direction of movement changes.

[0007] For example, patent CN 103863758 B, "Transition Mechanism for a Troughed Belt Conveyor," is known, with a priority date of December 11, 2012. This solution involves installing transition elements on the conveyor frame, each comprising a retaining plate, a side plate, and a bottom plate. The side and bottom plates are positioned at an angle so as to gradually form a transitional shape as the belt passes, providing a guiding and limiting effect on the belt. This solution is aimed at reducing friction and wear on the belt as it passes through the transition section. However, in this solution, the transition is formed primarily by fixed guide surfaces, rather than a system of rollers that create a smooth bend in the belt.In addition, it does not disclose an independent rigid bending and centering unit, in which both sides of the structure are connected to each other in a single coaxial spatial system, does not disclose the means for precise adjustment of the position of the belt in the transition zone, and does not disclose design measures that ensure the assembly coaxiality of the unit and reduce damage to the belt on the edges in the bending zone.

[0008] Also known is patent US 7967129 B2, "Centering Roller Support Unit for a Conveyor Belt with a Locking Mechanism," with a priority date of September 22, 2008. In this solution, belt centering is achieved by a roller support unit comprising a support, a roller frame, a roller, and a locking mechanism. The roller frame is mounted so as to be rotatable relative to the support, and its position can be locked in several angular positions. This solution allows for the correction of belt lateral drift by adjusting the position of the roller. However, this solution is primarily intended for regulating the direction of belt travel on straight sections of the conveyor and does not cover the belt bending unit in the transition zone between two conveyor sections located at an angle to each other.It lacks a set of rollers that work together to ensure smooth entry of the belt, the formation of its bend, and its retention in the working position precisely in the bending zone; it also lacks a rigid, two-sided design of the unit that ensures the alignment of the sides of the transition unit and reduces the serpentine movement of the belt.

[0009] Furthermore, patent US 7150352 B2 "Curved Belt Conveyor" is known, with a priority date of April 12, 2002. In this solution, the belt runs along a curved section along curved sidewalls and wraps around at least two rollers. A tracking roller is also provided, interacting with the lower section of the belt and mounted in an adjustable manner. This solution ensures that the belt passes along a curved path and tracks it in the turning zone. However, this solution pertains to a different type of curved conveyor, in which the belt moves along an extended arcuate path, rather than in a compact corner bend between two sections of the conveyor. It does not disclose the design of the unit that ensures the simultaneous formation of a local bend in the belt, rigid coaxial connection of the two sides of the unit, precise adjustment of the position of the belt in the transition zone and protection of the belt from cutting on the edges when operating under load.

[0010] The closest patent to the claimed invention is CN 223765303 U "Modular belt conveyor with a large angle of inclination", priority dated March 13, 2025. In this solution, a pressure mechanism is provided in the transition zone between the horizontal and inclined sections of the conveyor, including a corner unit mounted on a frame, wherein an upper pressure roller unit, a side limit roller unit and a lower pressure roller are located on the corner unit. Thus, in the closest solution, as in the claimed invention, there are features that coincide with the features of the claimed invention, namely: the presence of a transition zone between the sections of the conveyor; the presence of a corner unit installed in this zone; the presence of roller elements interacting with the upper, lower and side surfaces of the belt; the use of roller elements to hold the belt and reduce its deflection when passing the transition section.

[0011] However, the closest solution does not disclose the corner assembly as an independent, rigid bending and centering assembly, in which the side sections are combined into a single, coaxial structure with increased rigidity. It does not disclose the combination of retaining, supporting, adjusting, and tensioning rollers that work together not only to clamp and restrain the belt laterally, but also to smoothly enter the belt into the transition zone and form a smooth bend. Furthermore, the closest solution does not disclose how to implement connections that ensure a fixed relative position of the side sections and prevent their relative displacement, the use of special chamfered mounting bolts to align the assembly during assembly, or the rounded surfaces of the belt interface, which reduces undercutting and damage during operation under load.Consequently, the closest solution does not provide a sufficiently stable entry of the belt into the transition zone, stable maintenance of the coaxiality of the two sides of the unit, a reduction in the serpentine movement of the belt, a reduction in its roll-off, and a reduction in damage to the belt in the bending zone.

[0012] Thus, the technical problem is to create an independent conveyor belt bending and centering unit, which in the transition zone between sections of the conveyor would ensure not only a change in the direction of the belt movement, but also its smooth bending, stable entry, retention in the working position, coaxiality of the two sides of the structure, reduction of the serpentine movement and slippage of the belt, as well as reduction of damage to the belt on the elements of the unit when operating under load.

[0013] Disclosure of the essence of the invention

[0014] The technical problems are solved by creating a unit for bending and centering the belt of a Z-shaped conveyor, containing lateral load-bearing parts located on both sides of the belt, connected to each other by at least one integral connecting plate and at least one integral connecting element of a channel profile to form a rigid spatial structure that ensures mutual coaxiality of the lateral load-bearing parts.

[0015] The assembly comprises a system of rollers interacting with the belt in the transition zone, wherein said system includes retaining rollers for limiting lateral belt drift and maintaining its operating position relative to the lateral load-bearing parts, support rollers for supporting the load from the belt at the areas where it approaches and exits the bending zone, adjusting rollers for changing the position of the belt across the width of the assembly and ensuring its centering, and may additionally include tension rollers for creating and maintaining the required belt tension in the transition zone. The assembly also comprises corner rollers located in the bending zone of the belt and determining its required trajectory, forming a smooth bend.

[0016] At least some of the rollers are installed with the possibility of adjusting their position relative to the side bearing parts of the unit, due to which the required position of the belt in the unit is set, its position is adjusted during setup and the centered movement of the belt is maintained during operation.

[0017] In a particular embodiment, at least some of the corner rollers, which bear the increased load in the belt bending zone, are mounted on bearings.

[0018] The connections of the elements of the unit, determining the relative position of its lateral load-bearing parts, are made to ensure a fixed relative position of the said parts with the exclusion of their relative displacement relative to each other, and the surfaces of the elements of the unit, interacting with the tape in the zone of its bending, are made rounded.

[0019] The technical result consists in ensuring stable passage of the conveyor belt through the transition zone between sections of the conveyor.

[0020] The specified technical result is expressed in ensuring a smooth bend of the belt in the transition zone, stable entry of the belt, maintaining the position of the belt along the axis of movement, reducing the serpentine movement and slippage of the belt, as well as reducing damage to the belt in the bending zone.

[0021] This technical result is achieved by constructing the unit as an independent, rigid, spatial structure, in which the lateral load-bearing parts are connected by a solid connecting plate and a solid channel-section connecting element. This limits unwanted mutual displacement of the unit's sides, increases the rigidity of the structure, and ensures their alignment. This reduces the likelihood of misalignment of the transition zone, which causes lateral belt drift, serpentine belt motion, and uneven roller loading.

[0022] The placement of corner rollers in the transition zone provides not only support for the belt, but also a targeted change in its trajectory, creating a smooth bend in the transition zone between conveyor sections. This ensures that the belt enters the transition zone stably, without abrupt breaks or impacts with the unit components.

[0023] The ability to adjust the position of some rollers allows for precise alignment of the belt relative to the sides of the unit, compensates for deviations that occur during assembly and installation of the conveyor, and maintains the required belt alignment during operation. Furthermore, installing heavier-duty rollers on bearings reduces their overheating and wear during prolonged operation in the flexure zone.

[0024] The execution of connections of the unit elements with the provision of a fixed mutual position of the lateral load-bearing parts and the elimination of their mutual displacement relative to each other prevents the violation of the unit’s coaxiality, unstable movement of the belt and the increase of its lateral drift in the transition zone.

[0025] The rounded surfaces of the assembly elements interacting with the belt reduce the local load concentration on the belt in the bending zone and eliminate its cutting by sharp or smooth edges when operating under load, thereby increasing the durability of the belt.

[0026] Brief description of figures

[0027] Fig. 1 shows the Z-shaped conveyor belt bending and centering unit in disassembled form.

[0028] Implementation of the invention

[0029] The belt bending and centering unit of the Z-shaped conveyor is designed as an independent structural module, intended for placement in the transition zone between two conveyor sections located at an angle to each other and providing for the transfer of the belt from one direction of movement to another while simultaneously holding the belt in the working position and maintaining its centered run. The unit comprises lateral load-bearing parts (1) located on both sides of the belt, connected to each other by a connecting plate (2) and a connecting element of a channel profile (3). Retaining, supporting and adjusting rollers (4), corner rollers (5), as well as adjusting elements (6) and tension elements (7) are installed on the lateral load-bearing parts (1).

[0030] In one embodiment, the unit is installed in the lower transition zone between the lower section of the conveyor and the inclined section. In another embodiment, the unit is installed in the upper transition zone between the inclined section and the material infeed or discharge zone. One or two such units may be used in a single conveyor. The lower and upper units may be designed identically, mirror-symmetrically, or structurally similar, with the orientation of individual components changing depending on the direction of belt travel and the position of adjacent conveyor sections. This design allows for the use of a single corner unit design in both the lower and upper transition zones.

[0031] The unit comprises side load-bearing parts located on both sides of the belt. These side load-bearing parts may be formed as sheet metal cheeks, plate elements, bent elements, bent-welded elements, box-shaped elements, or a combination of these components. In a particular embodiment, the side load-bearing parts have a complex shape, including straight and curved sections corresponding to the belt's trajectory in the transition zone. To support operational loads, the side load-bearing parts may be equipped with reinforcing elements, including stiffeners, overlays, gussets, crossbars, crossbars, brackets, and welded or detachable reinforcing parts.

[0032] To unite both sides of the joint into a single rigid spatial structure, the lateral load-bearing portions are interconnected by at least one solid connecting plate and at least one solid channel-section connecting element. In particular embodiments, the connecting plate may be located at the bottom of the joint, in the middle of the joint, at the top of the joint, or simultaneously in two or more zones. Said connecting plate may be flat, spatially curved, bent, bent-welded, solid, or made with technological holes, if such holes do not reduce the required rigidity. The solid channel-section connecting element may be located transversely, longitudinally, inclined, or in another orientation that ensures a rigid connection of the lateral load-bearing portions.In specific cases, instead of one channel element, two or more profile connecting elements can be used, including channels, angles, rectangular pipes, box beams, bent sections, or a combination of them, provided that a single rigid spatial scheme of the node is maintained.

[0033] The fact that the connecting elements are made of one piece, linking both sides of the assembly into a single structure, increases the rigidity of the transition zone and maintains the alignment of its sides. Unlike designs in which each side essentially operates separately or rigidity is created primarily by the rollers themselves, in the proposed assembly, rigidity is created not only by the roller system, but primarily by the spatially integrated supporting structure. This reduces the likelihood of mutual displacement of the sides of the assembly, reduces distortion of the transition zone, stabilizes the position of the rollers relative to each other, and, as a result, reduces the causes of lateral belt drift and its serpentine movement.

[0034] The connections of the assembly elements, which determine the relative position of its lateral load-bearing parts, are preferably designed to eliminate any relative displacement of these parts. In certain embodiments, the load-bearing connections utilize round holes and fasteners, ensuring a fixed position of the elements after assembly. Belt position adjustment is achieved not by adjusting the play in the load-bearing connections, but by adjusting the position of the rollers and tensioning elements. This solution maintains the assembly's geometry constant, and fine-tunes the belt's movement using special adjustable elements, without compromising the rigidity and alignment of the structure.

[0035] The roller system of the assembly includes retaining, supporting, and adjusting rollers and, in certain embodiments, may additionally include tension rollers. The supporting rollers serve to support the belt load where it approaches and exits the bending zone. The retaining rollers limit lateral belt drift and maintain its operating position relative to the side load-bearing parts. The adjusting rollers are designed to change the position of the belt across the assembly width and to ensure its centering. The tension rollers, as well as the associated tensioning elements, are designed to create and maintain the required belt tension in the transition zone. Depending on the specific design, a single roller may combine the functions of supporting and retaining, retaining and adjusting, or supporting and tensioning.

[0036] In the illustrated embodiment, some of the rollers are located in the main portion of the belt approach to the transition zone and bear a relatively lighter load. Another portion of the rollers are located directly in the inflection zone, where the belt changes direction and experiences increased load. The unit also includes corner rollers located in the inflection zone. The corner rollers set the desired belt path, creating a smooth bend. This allows the belt path to change gradually, without a sharp break or impact with individual components of the unit.

[0037] Corner rollers can be arranged in pairs, sequentially, symmetrically or asymmetrically relative to the longitudinal axis of the belt, at the same or different levels, with the same or different pitches along the belt path. In one embodiment, one corner roller is installed on each side of the unit. In another embodiment, two or more corner rollers are installed on each side, operating sequentially. In yet another embodiment, one corner roller primarily determines the belt entry path, while the other compresses the belt at the point of its greatest deflection. The number of corner rollers, their diameter, location, and installation pitch are selected based on the belt width, the angle between adjacent conveyor sections, belt flexibility, the weight of the transported material, the belt speed, and the required smoothness of the bend.

[0038] In one preferred embodiment, the less loaded support rollers of the main portion of the assembly may be made of smaller-diameter rollers mounted on a shaft or axle without a separate bearing assembly, while the most heavily loaded rollers in the flexure zone are made of larger diameters and mounted on bearings. This ratio allows for a simpler design for rollers operating in relatively gentle conditions, while simultaneously increasing the service life of rollers bearing increased loads in the deflection and compression zones of the belt. However, in other embodiments, all rollers may be made of the same diameter, all rollers may be mounted on bearings, or individual rollers may have a different diameter, if required by calculations, operating experience, or the application conditions of a particular conveyor.

[0039] Rollers can be made of metal, polymer, or a combination of these. In some embodiments, the roller working portion can be made of steel, stainless steel, aluminum alloy, polymer material (including polyacetal), or a composite of these materials. The roller axle or shaft can be made of metal, and the outer working portion can be made of polymer. The roller working surface can be smooth, matte, textured, or have an anti-friction, wear-resistant, or protective coating. The choice of roller material is based on the abrasiveness of the material being transported, belt speed, required unit durability, operating conditions, and acceptable manufacturing costs.

[0040] At least some of the rollers are mounted so that their position can be adjusted relative to the side bearing parts of the assembly. Such adjustment can be accomplished using screws, bolts, eccentrics, slots, wedge-type fittings, levers, or a combination of these. In one embodiment, the roller is mounted on a bracket with oblong holes and moves after loosening the fasteners. In another embodiment, the roller is mounted on a bracket connected to a threaded tensioner, allowing for smooth adjustment of the roller's position without complete disassembly of the assembly. In yet another embodiment, the roller is mounted on a separate plate, fork, or frame, the position of which is adjusted using a pair of adjusting screws. Another embodiment is possible in which the adjustable roller position can be adjusted simultaneously in width, height, and angle, if required for precise belt alignment.

[0041] This adjustment allows the belt to be positioned at the desired location relative to the side sections of the unit, including the clearance from the side, thereby ensuring its centered movement. This is especially important when the conveyor is installed on a site with uneven levels, when adjacent sections of the conveyor experience slight spatial deviations after installation, or when changes in belt tension and position must be compensated for during operation. In one embodiment, the adjustment is present in both the lower and upper units, allowing belt positioning to be adjusted in different areas of the conveyor.

[0042] The unit's tensioning elements can be implemented in the form of threaded tensioners, studs with nuts, screw stops, turnbuckles, movable brackets that move relative to the base, or other mechanisms that allow the roller or group of rollers to be displaced, thereby changing the belt tension. Depending on the unit's layout, the tensioning elements can be located at the bottom of the unit, at the top of the unit, or on both sides of the unit. Tension adjustment can be individual for one roller, paired for two rollers, symmetrical for both sides of the unit, or grouped for several rollers on one side. In some cases, the tensioning elements are designed with fine adjustment capabilities, allowing for preliminary belt tensioning prior to conveyor installation and subsequent adjustment on-site.

[0043] In one embodiment, the assembly is welded. The side load-bearing parts, connecting plate, channel element, reinforcing parts, and other elements defining the assembly geometry are mounted on a jig or jig and joined by welding, maintaining specified angles and distances. This design ensures reproducible transition zone geometry, reduces the likelihood of underbending, overbending, and other deviations, and reduces the need for subsequent time-consuming belt adjustment. In another embodiment, the assembly may be partially welded and partially detachable. For example, the load-bearing part of the assembly may be welded, while the roller brackets, tensioners, housings, and individual service elements are detachable. A predominantly detachable design is also acceptable, in which the main elements are assembled using bolted, studded, or other fasteners, provided the required rigidity and alignment of the structure are maintained.

[0044] Special chamfered mounting bolts can be used to align assembly components during assembly. These bolts are temporarily inserted into the mating components of the assembly before the fasteners are fully tightened. This provides preliminary mutual alignment of the components and ensures their proper angular and plane positions. After alignment, the primary fasteners are finally tightened. These mounting bolts can be cylindrical with a leading chamfer, conical, stepped, guide, or other types that provide self-alignment when inserted into the mating holes. Their use is especially useful when assembling split or partially split versions of the assembly after transport to the operating site.

[0045] The surfaces of the unit components that interact with the belt in the bending zone are preferably rounded. This applies to both the working surfaces of the rollers and the edges of plates, guides, brackets, support elements, and other parts with which the belt contacts or may contact during the transition zone. Rounding can be achieved by bending, machining, flanging, welding, installing pads, installing replaceable protective strips, or other methods. In one embodiment, all edges of the components facing the belt are rounded. In another embodiment, only those areas located in the zone of greatest deflection and belt compression are rounded. This design reduces localized load concentration on the belt and prevents it from being cut by straight or sharp edges when operating under load.

[0046] The unit can be equipped with protective and maintenance elements. These elements include protective covers that shield the flexure zone and rollers from foreign objects, removable covers, hatches, and access openings for visual inspection of roller position, belt movement, and unit maintenance. In one embodiment, the cover serves only a protective function. In another embodiment, the cover simultaneously guides the flow of the transported material after it leaves the belt. Access openings and removable elements facilitate roller inspection, tensioner adjustment, and roller replacement, especially in the upper transition zone, where access to the unit may be limited.

[0047] The unit's geometric parameters are selected based on the specific conveyor's intended purpose. The angle between adjacent conveyor sections may vary. The unit's width is determined by the width of the belt used. The distance between the side bearing parts, the number of rollers, the roller diameter, the distance between rollers, the bracket length, the travel of the adjusting elements, and the tensioner parameters are selected to ensure stable belt passage through the transition zone, the formation of a smooth bend, and the prevention of belt damage. If necessary, the same unit design principles can be implemented in conveyors of smaller or greater width, in conveyors with a different inclination angle, as well as in equipment for transporting grain, seeds, compound feed, granulated materials, construction materials, and other materials.Changing the dimensions, the number of rollers, their diameter, the material of the rollers, the shape of the connecting plate, the number of channel elements, the configuration of the brackets and the method of tensioning does not change the essence of the invention, if the design of the unit as an independent rigid module is maintained, in which the roller system ensures a smooth entry of the tape, the formation of its bend and its centering in the transition zone.

[0048] The unit operates as follows. The belt approaches the transition zone along the first section of the conveyor and rests on support rollers. Upon entering the transition zone, the belt begins to interact with corner rollers, which set the desired trajectory and ensure a smooth bend. Concurrently, the retaining rollers limit lateral belt drift, while adjustable rollers allow for adjustment of the belt's position relative to the unit's side sections during setup and operation. Tension elements and tension rollers ensure the required belt tension and reduce sag in the bend zone. The transition zone maintains its specified geometry due to the rigid spatial connection of the side load-bearing sections, while the adjustable roller position ensures precise belt alignment, and the rounded contact surfaces reduce belt damage in the bend zone.As a result, the belt passes through the unit stably, with reduced serpentine running, lateral slip and uneven loading on the rollers.

[0049] In one embodiment, the unit is pre-configured before the conveyor is shipped to the customer, with the belt tension adjusted and the rollers set to a base position sufficient for normal operation on a level surface. In another embodiment, final adjustments are made at the conveyor's installation site, taking into account the actual position of the supports, base, and adjacent conveyor sections. The presence of adjustable rollers and tensioners allows for compensation for installation deviations without altering the geometry of the unit's supporting structure. In some cases, with sufficient manufacturing precision and when installed on a level surface, additional adjustments after installation may be minimal.

[0050] Thus, the conveyor belt bending and centering unit can be implemented in various design options, but in all of the specified options, a single result is achieved: the transition zone is formed by an independent rigid unit, in which a spatially linked supporting structure ensures the alignment of the sides, holding, supporting and adjusting rollers ensure the retention and centering of the belt, corner rollers ensure the formation of its smooth bend, and in the presence of tension rollers, the required tension of the belt is ensured when passing through the transition zone.

Claims

1. A Z-shaped conveyor belt bending and centering unit comprising side bearing parts located on both sides of the belt and a system of rollers interacting with the belt in the transition zone, including holding rollers for limiting the lateral drift of the belt and maintaining its working position relative to the side bearing parts, support rollers for taking up the load from the belt in the areas of its approach to the bending zone and exit from it, and adjusting rollers for changing the position of the belt across the width of the unit and for ensuring its centering, characterized in that the side bearing parts are connected to each other by at least one solid connecting plate and at least one solid connecting element of a channel profile with the formation of a rigid spatial structure that ensures mutual coaxiality of the side bearing parts, while the connections of the elements of the unit, determining the relative position of its side bearing parts,are made to ensure a fixed mutual position of the said parts with the exclusion of their mutual displacement relative to each other, and the unit also contains corner rollers that are located in the zone of the belt bend and set its required trajectory with the formation of its smooth bend, at least part of the rollers are installed with the possibility of adjusting their position relative to the lateral load-bearing parts, and the surfaces of the elements of the unit that interact with the belt in the zone of its bend are made rounded.

2. The unit according to paragraph 1, characterized in that the roller system additionally includes tension rollers for creating and maintaining the required tension of the belt in the transition zone.

3. The unit according to item 1, characterized in that the corner rollers are arranged sequentially along the trajectory of the belt in the transition zone.

4. The unit according to item 1, characterized in that the corner rollers are located in pairs on opposite sides of the belt.

5. The unit according to claim 1, characterized in that at least part of the corner rollers, which bear the increased load in the belt bending zone, are mounted on bearings.

6. The unit according to paragraph 5, characterized in that the rollers that bear the increased load in the belt bending zone are made with a larger diameter than the supporting rollers of the main part of the unit.

7. The unit according to paragraph 1, characterized in that the supporting rollers of the main part of the unit are mounted on a shaft or axle without a separate bearing unit.

8. The unit according to paragraph 1 or 2, characterized in that the adjusting and / or tensioning rollers are mounted on brackets connected to threaded tensioners.

9. The unit according to claim 1, characterized in that the lateral load-bearing parts are additionally connected to each other by at least one crossbar.

10. The unit according to paragraph 1, characterized in that the unit is welded.

11. The unit according to paragraph 10, characterized in that the elements of the unit that determine the geometry of the transition zone are connected by welding on a conductor.

12. The unit according to paragraph 1, characterized in that chamfered mounting bolts are used to align the elements of the unit during assembly.

13. The unit according to item 1, characterized in that the rounded surfaces are formed by rounded edges of plates, guides, brackets and / or working surfaces of rollers.

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