METHOD FOR MANUFACTURING A CLEANING ROLLER AS WELL AS A CLEANING ROLLER AND VACUUM NOZZLE

Description

[0001] The invention relates to a method for producing a cleaning roller, in particular for a floor cleaning device. The cleaning roller comprises a roller body and a cleaning assembly arranged on the roller body.

[0002] Cleaning rollers are cleaning elements that are moved by a rotational movement relative to a surface to be cleaned. For this purpose, cleaning rollers are usually coupled to a drive that enables continuous, oscillating, and / or intermittent rotation.

[0003] The invention is based on a cleaning roller that is functionally divided into a roller body and a cleaning assembly arranged on the roller body. The roller body is responsible for the structural integrity of the cleaning roller and its shape, while the cleaning assembly is intended for contact with the surface to be cleaned and thereby produces the actual cleaning effect.

[0004] The cleaning arrangement can, in particular, comprise textile cleaning elements such as cloths, fabrics, and / or nonwovens. Furthermore, liquid-retaining structures such as sponges or foams, or liquid-draining elements such as sealing lips, are also known. Another common design includes structures with protruding free fiber ends or loops, such as plush or bristle strips. These and other cleaning elements can also be combined with one another within a cleaning arrangement.

[0005] Cleaning rollers are frequently used in floor cleaning devices such as vacuum cleaner nozzles, brush attachments, or robot vacuum cleaners. Their task—particularly in textile floor coverings—is to mechanically loosen adhering and / or embedded dirt particles so that they can be removed by a suction air stream and / or the action of a cleaning fluid.

[0006] The general structure of a cleaning roller with an attached drive element is known from DE 199 61 008 A1.

[0007] US 2004 / 0 010 875 A1 discloses a method for manufacturing a cleaning roller in which a metal shaft is overmolded with a plastic. DE 10 2015 102 610 A1 shows a brush roller with a roller body coated with a polymeric protective layer. WO 2009 / 149 722 A1 shows a cleaning roller with multiple plastic layers.

[0008] The structural component of the roller body is usually made of plastic for cost reasons. Plastic injection molded parts are the most common. The roller body is formed in a hollow mold, which is then filled with a molten plastic.

[0009] Due to the high mechanical stresses encountered by a cleaning roller, the roller bodies must have a certain size and mass. However, this complicates production using the plastic injection molding process. Due to the large polymer mass, excessively rapid and / or uneven cooling of the polymer material can lead to stress and / or deformation of the plastic part. This not only impairs the external appearance but can also impair the function of the cleaning roller.

[0010] In addition to compromising structural integrity due to intrinsic stresses or, potentially, stress cracks, such a deformed cleaning roller can also be detrimental during operation. The irregularities can lead to uneven weight distribution on the cleaning roller, resulting in an imbalance during rotation. This, in turn, leads to uneven loading of the cleaning roller, its bearings, and drive. Imbalances also cause annoying vibrations during use, which can be irritating to users.

[0011] To avoid temperature-related distortion in large-volume injection-molded parts, particularly uniform—i.e., slow—cooling is required. However, this results in longer cycle times, which can make production increasingly unprofitable.

[0012] Against this background, the invention is based on the object of providing an improved manufacturing method for a cleaning roller, which enables the efficient production of dimensionally accurate cleaning rollers. The subject matter of the invention and the solution to this object are a method according to claim 1. Preferred embodiments are specified in the dependent subclaims. Furthermore, the invention relates to a cleaning roller according to claim 18 and a vacuum cleaner nozzle according to claim 19.

[0013] Based on the generic method, the invention provides that the roller body has a core and a shell arranged around the core, and that the roller body is manufactured in a multi-stage injection molding process. The core is manufactured in a first injection mold using a first polymer material, and the shell is manufactured by at least one subsequent overmolding of the core in a second injection mold using a second polymer material. By dividing the injection molding process into at least two separate processes, the mass of plastic melt used can be reduced in each case. This allows for faster solidification / cooling without excessive temperature differences occurring within the component.

[0014] Overmolding refers to an injection molding process in which the overmolded component, e.g., the core, is placed into an injection mold, particularly the second injection mold, where it is encased in a melt, particularly of the second polymer material, and subsequently solidifies. The melt preferably completely fills the cavity formed between the component and the injection mold.

[0015] The core produced in the first injection molding step can, in particular, be actively cooled to achieve the fastest possible solidification and temperature equalization. Active cooling can be achieved within the injection mold and / or by subsequent exposure to a coolant—in particular, cooling air. Even if deformations, shrinkage, and / or cracks occur during such active cooling, these can be compensated or filled during the production of the shell in the second injection molding step. Despite the time advantage, the roller body produced using the method according to the invention can achieve an injection molding quality and dimensional accuracy that can only be achieved with complex temperature control during the cooling process for such large plastic components.

[0016] The first injection mold and the second injection mold—and possibly additional injection molds—can be formed in a single injection molding tool using various different so-called "mold cavities." This makes it particularly easy to implement shared temperature control and injection molding material feeding. During a cycle, all injection molding steps can then be performed simultaneously in the same injection molding tool.

[0017] Within the scope of the method according to the invention, it is preferably provided that the jacket is also manufactured in several stages, with at least one further overmolding in a further injection mold using a further polymer material. The jacket then has at least one inner jacket produced in the second injection molding step and an outer jacket produced in a further injection molding step.

[0018] Preferably, exactly one additional injection molding step is provided, so that the production of the roller body comprises a total of three injection molding steps: core, inner shell, and outer shell. At least the inner shell and core, as well as the outer shell and core, are directly connected to one another, flatly and with a material bond.

[0019] Preferably, active cooling is provided in one or more injection molding steps—except for the outermost layer of the shell. The outermost layer can be used for surface finishing and to compensate for any inaccuracies in the base layer formed by the core and the underlying layers of the shell.

[0020] Alternatively or additionally, the outer layer can be manufactured in several alternatively selected second or additional injection molds. This alternative selection allows roller bodies with different (external) geometries to be manufactured. These roller bodies can be adapted, in particular, to different cleaning arrangements. This could involve, for example, different fittings on a bristle roller. As a further option, this could enable adaptations, for example, between a wet cleaning roller (e.g., with sponge elements and wiper strips) and a dry cleaning roller (e.g., with plush and / or bristle strips).

[0021] According to a preferred embodiment, the composition of the first polymer material corresponds to at least 95% by weight with the composition of the second polymer material. The process according to the invention involves producing the roller body in multiple parts or layers in order to compensate for temperature- or cooling-induced distortions and / or shrinkage cracks. To achieve this objective, it is helpful for the first polymer material to have particularly similar physical and chemical properties. Ideally, the end product should be externally indistinguishable from a component manufactured in a single injection molding step—with greater effort and a longer process time. The chemical similarity of the two polymer materials is particularly beneficial for ensuring good cohesion between the core and the shell.

[0022] According to a preferred embodiment of the invention, the first polymer material and / or the second polymer material comprises at least 50 wt.% of a polymer selected from the group polystyrene (PS), acrylonitrile butadiene styrene (ABS) and polypropylene (PP).

[0023] Particularly preferably, the first and second polymer materials are identical—i.e., they have the same plastic composition. In addition to the advantages for the product, this can also simplify the design of the system used to carry out the process according to the invention. For example, the feed and / or heating and extrusion unit for the first polymer material and the second polymer material can be implemented together. Particularly preferably, only a single extrusion unit is provided, which can selectively or simultaneously feed plastic melt to the first injection mold and / or the second injection mold.

[0024] According to a further preferred aspect of the invention, the first polymer material and the second polymer material have the same density. This can be achieved trivially with identical polymer materials or, alternatively, with different polymer blends. By using polymer materials of the same density, the weight distribution within the roller body is independent of the shape of the core overmolded by the jacket. Even with significant deformation of the core during or after the first injection molding step, there are no disadvantages with regard to the position of the center of gravity and the moments of inertia of the cleaning roller. Production tolerances during core manufacture cannot therefore lead to unintentional imbalances in the cleaning roller.

[0025] Preferably, the core undergoes a cooling phase before being overmolded with the second polymer material—i.e., between the first injection-molding step and the second injection-molding step. During this phase, the temperature of the preformed core is further reduced, so that it can serve as an additional temperature sink during overmolding with the second polymer material to cool the second polymer material.

[0026] Typically, injection-molded parts have an (external) temperature of approximately 200 °C upon leaving the injection mold. According to a particularly preferred variant, the cooling phase is dimensioned and designed such that the core cools to a (surface) temperature of no more than 160 °C, i.e., by at least 40 °C. A particularly advantageous external surface temperature of the core before the second injection molding step is between 145 °C and 155 °C.

[0027] According to a preferred embodiment, the cooling phase takes place within the first injection mold. This mold can be appropriately tempered for this purpose, if necessary.

[0028] According to a further preferred embodiment, the cooling phase takes place at least partially outside the injection mold. For this purpose, the core can additionally be exposed to a cooling medium - for example cooling air. This has the advantage that the first injection mold does not have to be separately tempered to achieve the cooling. Cooling can also be further accelerated by controlling a flow of the cooling medium. Any negative side effects of (excessively) rapid cooling can subsequently be easily compensated for by the multi-stage injection molding process. Another advantage is that the first injection mold can be used to form another core after the core has been removed. This increases the throughput of a production line.

[0029] One aspect of the invention is that the cooling of the shell can be accelerated within the scope of the inventive method, since the already cured—and optionally additionally cooled—core, as an internal heat sink, can accelerate the cooling of the shell. To optimize this aspect, it is preferably provided that the first polymer material (of the core) and the second polymer material (of the shell) are in a mass ratio between 1:2 and 2:1. A mass ratio of 1:1—or 1:1:1 in a three-stage process—has proven particularly preferred.

[0030] According to a preferred embodiment, the roller body is formed around a rotational axis, wherein it has a greater, in particular five times greater, longitudinal extension in the direction of the rotational axis (axial direction) than in the radial direction perpendicular to the rotational axis (radial extension). The cleaning roller or the roller body are designed and provided to be set in rotation about the rotational axis. The cleaning roller as a whole and the roller body in particular are designed such that the rotational axis passes through their respective centers of gravity. Thus, at least first-order imbalances are avoided during a rotational movement.

[0031] The roller body preferably has a maximum diameter between 1.5 cm and 4 cm. With such an extension, dimensionally accurate production as a solid part in a single-stage injection molding process is very difficult. The roller body preferably has a length measured in the axial direction between 20 cm and 35 cm.

[0032] According to a preferred variant of the method, cleaning elements of the cleaning arrangement, in particular bristles or tufts of bristles, are molded into the casing in a form-fitting manner. This ensures that the cleaning elements are held captively to the roller body. Subsequent separate fastening, such as by gluing or welding, is not necessary.

[0033] For this purpose, it is particularly provided that the cleaning elements are clamped in the second and / or a subsequent injection mold and are overmolded in one work step at the same time as the inserted core - and, if necessary, an intermediate jacket.

[0034] The core preferably has an outer side and at least one form-fitting arrangement formed on the outer side. The sheath engages in this form-fitting arrangement. The form-fitting arrangement can, in particular, have projections and / or recesses. The form-fitting connection between the sheath and core ensures that they are captively and rigidly coupled to one another, even if a material-to-material connection cannot be established between the first polymer material and the second polymer material.

[0035] Advantageously, at least one handling aid is inserted into the first injection mold before the core is produced, which can be removed non-destructively from the roller body after the shell has been produced. This can be a metallic rod, in particular, which is overmolded with the first polymer material in the first injection mold. After the first injection mold is opened, the material can be removed from the mold using the handling aid. The handling aid then facilitates correct (central) positioning within the second injection mold. This ensures uniform, circumferential overmolding of the core with the second polymer material.

[0036] After the second injection molding step (and possibly further injection molding steps), the handling aid can be removed—in particular, pulled out—from the roller body without causing any damage. It can then be reused in the production of a subsequent roller body. After the removal of the handling aid, a cavity remains in the roller body, which is particularly preferably filled with a polymer material in a subsequent step. For this purpose, the injection mold from the last injection molding step of the shell can be used, in particular, whereby any openings in the injection mold for the handling aid must be covered.

[0037] Preferably, within the scope of the method according to the invention, a functional unit, for example a rolling bearing, is captively cast. For this purpose, it is provided, in particular, that a receptacle is formed on the core into which the functional unit can be inserted after the first injection molding step. By overmolding the core with the second polymer material, the functional unit is subsequently fixed by a form fit such that removal is no longer possible.

[0038] Within the scope of the method according to the invention, it is provided that the core is overmolded with the second polymer material. After the second injection molding step, the solidified second polymer material surrounds the core circumferentially and preferably, but not necessarily completely. According to a particularly preferred embodiment, the core can also be partially lined by the shell. For example, the core forms at least one receptacle accessible in the axial direction, which is lined by the shell. This can, for example, be a receptacle for an axial guide mandrel, which is inserted into the axial end of the cleaning roller during normal use. Very particularly preferably, at least one rolling bearing is arranged within the receptacle and is held therein in a form-fitting manner by the part of the shell lining the receptacle.

[0039] At least one drive element, in particular a gear, is expediently mounted on the core. This can be mounted particularly after the first injection-molding step, after which the drive element is subsequently held captively in the roller body by the casing in the second injection-molding step. This is particularly expedient for drive elements that are arranged at a distance from the axial ends of the roller body.

[0040] The core has at least one retaining element for a torsionally rigid coupling to the drive element. According to the invention, this retaining element is a non-metallic retaining part, such as a metal clamp or metal plate. The retaining element improves the transfer of torque to the core—and thus to the entire roller body.

[0041] The invention also relates to a cleaning roller, in particular for a vacuum cleaner floor nozzle, obtainable according to the manufacturing method described above. The cleaning roller comprises a roller body and a cleaning assembly arranged on the roller body. According to the invention, the roller body has a core made of a first polymer material and a shell directly surrounding the core made of a second, in particular identical, polymer material. Due to the at least two-shell structure, the cleaning roller according to the invention has greater stability and dimensional stability. It is therefore particularly well suited for heavy-duty use and long service lives.

[0042] A further aspect of the invention relates to a vacuum cleaner floor nozzle with such a cleaning roller. The vacuum cleaner nozzle has a housing with a suction nozzle arranged on the underside and a brush chamber arranged within the housing and adjoining the suction nozzle. The cleaning roller according to the invention is arranged within the brush chamber and coupled to a drive. This drive serves to set the cleaning roller in a rotary motion. The drive can be represented in particular by an electric motor or an airflow turbine. The high stability and dimensional accuracy of the cleaning roller as a result of the manufacturing method according to the invention enables high speeds and a good cleaning effect.

[0043] The invention is explained below with reference to figures illustrating only one exemplary embodiment. They show schematically: Fig. 1A shows a longitudinal section through the core and the first injection mold, Fig. 1B shows a side view of the core produced in the first injection molding step, Fig. 2A shows a longitudinal section through the cleaning roller according to the invention in the second injection mold and Fig. 2B shows a side view of the cleaning roller according to the invention.

[0044] According to the method according to the invention, a roller body 1 for a cleaning roller is produced in a multi-stage injection molding process. Fig. 1A As can be seen, a core 3 is first produced with a first polymer material in a first injection mold 2. The first injection mold 2 is formed in several parts, wherein Fig. 1A At least four segments 2a to 2d are visible. A T-shaped rod 4 is inserted in the end region as a handling aid for transporting the core 3 between the injection molds. This rod is enclosed by the polymer material of the core 3, but can be removed from the roller body 1 at a later time without causing damage by pulling it out longitudinally.

[0045] Again Fig. 2A According to the invention, the core 3 is then overmolded with a first polymer material in a second injection mold 5 with a jacket 6. The sectional view shows that the jacket 6 completely encloses the core 3 on the outside. The result of this second injection molding step is the Fig. 2B The roller body shown here has slot-shaped receptacles 7 on its outer surface, into which a cleaning element—in particular a bristle strip—can be subsequently inserted and fixed, for example, by gluing.

[0046] To ensure good cohesion between the sheath 6 and the core 3, as well as a uniform mass distribution, the core 3 and the sheath 6 are made of the same polymer material—that is, in particular, with the same density. In the illustrated embodiment, the mass of the sheath 6 accounts for approximately two-thirds of the mass of the core 3.

[0047] The roller body 1 as a whole (as well as the core 3 and the shell 6) are formed around a rotation axis x. The roller body 1 has a longitudinal extension l in the direction of the rotation axis x (axial direction), which is approximately ten times greater than the transverse extension d perpendicular to the rotation axis x. Due to the symmetrical design of the roller body 1 with respect to the rotation axis x, the rotation axis x runs through its center of gravity.

[0048] How to Figuren 1A und 1B can be seen, on the outer side 3a of the core 3, form-locking arrangements in the form of extensions 8 are formed, which in the second injection molding step ( Fig. 2A ) are encompassed by the casing 6 in a form-fitting manner.

[0049] In order to support the roller body 1 during its later intended use - in particular within a vacuum cleaner nozzle - bearing pins 10 are inserted into end receptacles 9 of the core 3 after the first injection molding step, which bearing pins are cast around by the casing 6 in the second injection molding step and are thereby fixed within the roller body.

[0050] Again Fig. 2B As can be seen, a gear 11 is inserted as a drive element, spaced apart from the end regions 1a, 1b of the roller body 1. For this purpose, holding elements 12 in the form of metallic holding plates were cast into the core 3 in the first injection molding step. The gear 11 was pushed onto these in the axial direction x between the first injection molding step and the second injection molding step. Through the subsequent encapsulation with the casing 6, the gear 11 is also held captively in the roller body 1 as a drive element.

Claims

1. A method for producing a cleaning roller, in particular for floor cleaning equipment, comprising a roller body (1) and a cleaning assembly arranged on the roller body (1), wherein the roller body (1) has a core (3) and a jacket (6) arranged around the core (3), characterized in that the roller body is produced in a multi-stage injection molding process, wherein the core (3) is produced in a first injection mold (2) with a first polymeric material and wherein the jacket (6) is produced by means of at least a subsequent overmolding of the core (3) in a second injection mold with a second polymeric material, that at least one drive element (11) is attached to the core (3) and that the drive element (11) is subsequently captively held in the roller body by means of the jacket (6), that the core (3) has at least one holding element (12) for the rotationally rigid coupling to the drive element (11) and that the holding element (12) is a holding part of a different material, which is placed into the core (3) .

2. The method according to claim 1, characterized in that at least 95 % by weight of the composition of the first polymeric material corresponds to the composition of the second polymeric material.

3. The method according to claim 2, characterized in that the first polymeric material is identical to the second polymeric material.

4. The method according to one of claims 1 to 3, characterized in that the first polymeric material has the same density as the second polymeric material.

5. The method according to one of claims 1 to 4, characterized in that the core (3) passes through at least one cool-down phase prior to the overmolding with the second polymeric material.

6. The method according to one of claims 1 to 5, characterized in that the first polymeric material and the second polymeric material have a mass ratio of between 1 : 2 and 2 : 1.

7. The method according to one of claims 1 to 6, characterized in that the roller body (1) is formed around an axis of rotation (x) and that the roller body (1) has a greater, in particular five times greater, longitudinal extension (1) in the direction of the axis of rotation (x) than in the radial direction perpendicular to the axis of rotation.

8. The method according to claim 7, characterized in that the axis of rotation (x) runs through the center of gravity of the roller body (1).

9. The method according to one of claims 7 or 8, characterized in that the roller body (1) has a maximum diameter (d) of between 1.5 cm and 4 cm.

10. The method according to one of claims 7 to 9, characterized in that the roller body (1) has a length (1) of between 20 cm and 35 cm measured in the axial direction (x).

11. The method according to one of claims 1 to 10, characterized in that cleaning elements of the cleaning assembly, in particular bristles or tufts, of bristles are cast in a positive manner into the jacket (6).

12. The method according to one of claims 1 to 11, characterized in that the core (3) has an outer side (3c) and at least one positive locking assembly (8), which is formed on the outer side and with which the jacket (6) engages in a positive manner.

13. The method according to one of claims 1 to 12, characterized in that at least one functional unit, in particular a rolling bearing, is cast in a captive manner into the roller body (1).

14. The method according to one of claims 1 to 13, characterized in that at least one receptacle, which is accessible in the axial direction (x) and which is lined by the jacket (6), is formed in the core (3).

15. A cleaning roller, in particular for a vacuum cleaner nozzle, which can be obtained according to a method according to claims 1 to 14, comprising a roller body (1) and a cleaning assembly arranged on the roller body, wherein the roller body has a core (3) with a first polymeric material and a jacket (6) directly surrounding the core with a second, in particular identical polymeric material, characterized in that at least one drive element (11), which is captively held in the roller body by means of the jacket (6), is attached to the core (3), that the core (3) has at least one holding element (12) for the rotationally rigid coupling to the drive element (11) and that the holding element (12) is a holding part of a different material, which is placed into the core (3).

16. A vacuum cleaner nozzle, characterized by at least one cleaning roller (1) according to claim 15.