Flexible Hose, more Particularly Vacuum Cleaner Hose, Method for Production of Same and Device Which can be Used Herefor

A flexible hose (10), for a vacuum cleaner, has a wall (12), an inner side (14) of which delimiting a cavity (16) for conveying media and at least one outer side (18) of which having a profiling (20) which has, in section, seen along a longitudinal axis (22) of the hose, elevations (24) and depressions (26). On the outer side of the wall, at least one electrically conductive track (28) is provided which extends around the wall and is in electrical contact with at least one electrically conductive thread (30) which electrically connects ends of the hose facing away from one another. The electrically conductive thread is fastened to the outer side in a manner extending substantially along the longitudinal axis of the hose and transverse to the electrically conductive track.

TECHNICAL FIELD

The present invention relates to a flexible hose according to the preamble portion of claim1as well as to a method for production of such a hose in large quantities and to a device usable for that purpose. In particular, the invention relates to a flexible vacuum cleaner hose and the production thereof, such as used on a large scale in an industrial environment, in trades and in private households.

BACKGROUND OF THE INVENTION AND PRIOR ART

In the suction or conveying of very fine particles by a hose consisting of a plastics material, such as, for example, polyethylene (PE), polypropylene (PP) or an ethylene vinyl acetate co-polymer (EVAC), for example by a vacuum cleaner, strong electrostatic charges are generated by the friction of the particles against the walls of the hose. These can abruptly discharge, sometimes even with formation of sparks, in the event of, for example, contact of the electrically charged suction hose with an earthed component or user. The discharges can be of such strength that damage occurs at electronic apparatus and/or sharp pain is triggered at the user, in the worst case a risk to life arising if, for example, a heart pacemaker is brought to a stop.

Moreover, spark discharges can ignite explosive dust/air mixtures, gas/air mixtures and solvent-vapor/air mixtures. A risk of electrostatic ignition can in that case arise not only from the charged conveyed material, but also from charged components of a vacuum cleaner, particularly the suction hose.

Such sudden discharges can be prevented if all parts, which conduct the particles, of the vacuum cleaner are electrically connected with one another for potential equalization and with a protective conductor of the associated electrical connector.

Against this background, use is increasingly made of suction hoses consisting of a highly resistive, electrically conductive material, for example PE, in which fine carbon particles are embedded, for suction of fine dusts. However, this material is expensive by comparison with pure PE and, moreover, leaves behind undesired abrasion tracks if the suction hose is drawn by its outer circumferential surface over a substrate. These abrasion tracks can be prevented by an additional protective layer applied to the outer circumference of the hose, but this is connected with additional cost and makes the suction hoses more expensive.

In order to create a remedy it has been proposed in document DE 20 2009 016 596 U1 to use a coiled suction hose of an economic basic material at which is provided at least one electrical conductor, which extends substantially over the coil length of the suction hose, for dissipation of electrostatic charge, wherein the electrical conductor has a width at most equal to the channel width of the suction hose. This electrical conductor can be formed as, for example, a plastics material layer with an embedded carbon component, as an electrically conductive wire extending helically or as an electrically conductive strip. With respect to the position of the electrical conductor, it can be inferred from this prior art that the electrical conductor is either embedded in the material of the suction hose or arranged at the inner side of the base of the helix channel, at the outer side of the base of the helix channel or inwardly or outwardly at the webs bounding the helix channel.

Document DE 296 02 061 U1 discloses a further electrically dissipative hose with helically extending wave crests and wave valleys adjacent thereto at its outer side. An outwardly stripped electrical conductor consisting of an uninsulated wire suitable for dissipation of electrostatic charges is deposited in the wave valleys. The electrical conductor is covered by a strip which consists of thermoplastic material and the longitudinal edges of which are fastened to the flanks of the wave crests by welding or glueing.

Further, in order to enable, in particular, improved dissipation of electrical charges by comparison with the afore-described hoses, which comprise a “single electrically conductive device”, a conveying hose has been proposed in document WO 2005/047748 A1, in which a combination of “two electrically conductive devices” for conducting away electrical charges is provided. One electrically conductive device is a region, which concentrically surrounds the interior of the hose and is bounded by the inner surface, of the hose wall, which through embedding of electrically conductive particles in the basic material is furnished with an electrical conductivity significantly increased by comparison with the basic material. The other electrically conductive device is a local electrical conductor element which extends in axial direction and which is directly connected with the region of increased electrical conductivity and is to conduct away charges, which are collected by this region, to ground.

In the case of the pressure hoses according to this prior art the two electrically conductive devices are directly embedded in the hose wall during extrusion or co-extrusion of the respective pressure hose, so that a one-part ready-to-use pressure hose is created in one work step.

On the other hand, a widely used practice, which is particularly preferred with respect to a satisfactory capability of maintaining shape under an internally prevailing vacuum, for producing flexible suction hoses consists of initially extruding a profile of a plastics material, which is then wound helically or spirally, wherein adjacent coils or windings of the profiles are welded or glued together. In this connection, for example, document WO 2012/160524 A1 discloses a flexible plastics material hose produced by winding an extruded profile, wherein electrical conductors can also be embedded in the profile during extrusion of the profile.

Finally, a flexible hose having an outer wall produced from a plurality of windings of an extruded and helically wound profile is known from document DE 20 2017 107 890 U1, which defines the preamble portion of claim1. Adjacent windings of the profile are connected together by a seam, wherein the outer wall has an electrically conductive track which contains a conductive section of the extruded and helically wound profile and/or the seam. In that case, the conductive section consists of an electrically conductive plastics material. The electrically conductive track additionally contains an electrically conductive thread, which at the outer wall of the hose is in electrical contact with the conductive section of the extruded and helically wound profile and/or the seam and, in particular, is embedded in the seam or in a groove provided in the profile. This electrically conductive thread is thus similarly a helically-wound integral component of the finished suction hose.

A disadvantage of the previously known electrically dissipative flexible hoses with “doubled dissipation” resides in the fact that for a good electrical dissipation capability of the hose a comparatively large amount of electrically conductive materials has to be provided in the hose, which materials due to integration thereof in the hose are also very difficult to recover, if at all.

Object

Starting from the prior art according to document DE 20 2017 107 890 U1 the invention has the object of developing a flexible hose, particularly a vacuum cleaner hose, in such a way that the hose has a good dissipation capability for electrostatic charges, yet the problems discussed above in this connection with respect to the prior art are addressed. In particular, the electrically dissipative flexible hose with use of a comparatively small amount of electrically conductive materials shall have improved suitability for recycling. The object of the invention further comprises indication of a method for production of such an electrically dissipative flexible hose and a device for application of an electrically conductive thread to such a hose, which enables production or partial making-up—which is as simple, quick and economic as possible—of the hose with at least one electrically conductive thread in large quantities.

Illustration of the Invention

These objects are fulfilled by a flexible hose, particularly vacuum cleaner hose, with the features of claim1, a method for producing a flexible hose by the method steps of claim11and a device for application of an electrically conductive thread to an outer side of a flexible hose with the features of claim16. Advantageous embodiments of the invention are the subject matter of the dependent claims.

According to the invention, in a flexible hose, particularly vacuum cleaner hose, having a wall which by an inner side delimits a cavity for the conveying of media and has at least at an outer side a profiling which as seen in section along a longitudinal axis of the hose has a wave shape with elevations and depressions, wherein provided at the outer side of the wall is at least one electrically conductive track extending around the wall and disposed in electrical contact with at least one electrically conductive thread electrically connecting mutually remote ends of the hose, the electrically conductive thread extends substantially along the longitudinal axis of the hose and transversely to the electrically conductive track and is secured to the outer side of the wall.

In other words, the electrically conductive thread—by contrast with the prior art discussed above—is not laid in the circumferential direction of the hose, but extends in longitudinal direction of the hose according to the invention, in which case it crosses the encircling electrically conductive track while producing an electrical contact and thus quasi an electrical short-circuit. Electrostatic charges collected in the electrically conductive track as a “first electrically conductive device” are thus conducted away directly via the electrically conductive thread as a “second electrically conductive device” to the ends of the hose.

Since the electrical conductive thread at the wall of the hose according to the invention does not encircle the longitudinal axis thereof, but as seen in plan view extends along or substantially parallel to the longitudinal axis of the hose, less electrically conductive material for this second electrically conductive device is needed by comparison with the prior art outlined above. This is not only of advantage with respect to a comparatively low electrical resistance, but is also accompanied by advantages in cost and weight.

This possibility of influencing on the electrical resistance of the hose by the electrically conductive thread constructed or arranged in accordance with the invention can also have the effect, depending on the respectively desired or required capability of electrical dissipation, of differently distributing the individual resistances of track and thread, for instance to reduce the electrical dissipation capability of the electrically conductive track, for example by reduction in the carbon content in a plastics material—which is made electrically conductive by addition of carbon—for the electrically conductive track, which similarly offers cost advantages.

Moreover, since the electrically conductive thread has been mounted on the outer side of the wall it is simpler—again by comparison with the prior art discussed in the introduction, in which all electrically conductive devices are integrated in the hose, more precisely in the wall thereof—to remove the electrically conductive thread of a hose, which is to be discarded, from the rest of the hose for recycling purposes.

Not least, the construction of the hose according to the invention advantageously allows, in the manufacture thereof, a (at least) two-stage procedure in which initially a basic hose with the electrically conductive track is produced as a first electrically conductive device before—only in a second step—this basic hose is enhanced with respect to an improved capability of electrical dissipation by application of the electrically conductive thread as a second electrically conductive device. As a consequence of this modular construction of the hose it is thus possible to produce hoses as desired or required with different electrical dissipation capability from a form of kit, which ensures a high degree of flexibility in hose production and also offers cost advantages.

The term “electrically conductive thread” here represents the most general understanding of an electrical conductor, the length dimension of which is very much greater than its width dimension and thickness dimension. In that case, the “thread” can in principle also be at the same time an electrical conductor and fastening measure, such as is the case, for example, with a narrow adhesive tape made electrically conductive or an adhesive made electrically conductive and coated in a narrow longitudinal track, be it—depending on the kind of hardening taking place—for example a two-component or multi-component adhesive, an adhesive reacting under visible light or ultraviolet light or of thermoplastic nature (hot-melt adhesive).

If the electrically conductive thread and the fastening member for it are two components, it is basically possible to lay the electrically conductive thread on the profiling of the hose and then or thereafter to conceal or coat it by, for example, a hot adhesive, an ultraviolet adhesive or an ultraviolet lacquer or a track of an appropriately reacting or setting synthetic material foam or casting resin. On the other hand and particularly with respect to production economically and with process reliability it is, however, currently preferred if the electrically conductive thread is secured to the outer side of the wall by an adhesive strip. In an advantageous embodiment the adhesive strip can in that case cover the electrically conductive thread to both sides as seen in circumferential direction of the hose, which is conducive to a best possible in-contact retention of the electrically conductive thread at the electrically conductive track.

Moreover, provision can be made for the electrically conductive thread or the adhesive strip, which covers the electrically conductive thread, to be surrounded at the outer side of the wall—in a given case as a further enhancement—by a braiding of the hose. In that regard the braiding can advantageously serve as (an additional) securing and/or as (a further) protection of the electrically conductive thread at the outer side of the wall of the hose. In an appropriate embodiment of the device for braiding of the flexible hose it is also possible to apply and secure the at least one electrically conductive thread to the outer side of the wall during the braiding. A combination of fastening of the electrically conductive thread by an adhesive strip and braiding of the hose presents itself particularly when the application of the electrically conductive thread and the braiding take place at different locations and/or at different times.

In principle, it is possible to provide the electrically conductive track at any position on the outer side of the wall of the hose as long as it is ensured that the at least one electrically conductive thread can electrically contact and short-circuit the electrically conductive track. However, it is preferred, particularly with respect to an easiest and most reliable possible contacting of the electrically conductive track by the electrically conductive thread, if the electrically conductive track is formed on the outer side of the wall near to or at the elevations of the profiling.

In an advantageous embodiment of the flexible hose provision can additionally be made for the hose to be provided at one or both of the mutually remote ends with a hose mounting member of an electrically conductive material, optionally also as an adapter, which at the finished hose preferably rotatably retains a further connecting piece with, for example, a cone or bayonet to guarantee correct hose connection with associated terminal equipment (for example a vacuum cleaner) or tool. It is then possible by way of the hose mounting member and the connecting piece optionally mounted thereon to transfer to the terminal equipment and the grounding thereof electrostatic charges collected by the electrically conductive track of the hose and, in particular, transferred by way of the electrically conductive thread to the hose ends, and thus conduct away or remove those charges. The hose mounting members and/or the connecting pieces mounted thereon can if required additionally be provided with metallic contacts. In a corresponding embodiment of the hose mounting members and/or the connecting pieces mounted thereon it is also advantageously possible for electrostatic charges to be conducted away via the hose to terminal equipment such as, for example, a vacuum cleaner, which charges occur, for example, during an abrading or polishing process at/in an abrading machine. This can be of interest especially when the machine itself does not have an earthed mains connection or alternatively is driven by compressed air or with use of battery technology.

The following two variants, in particular, present themselves for attaching the afore-mentioned hose mounting members to the hose ends: In the first variant, when the profiling of the hose at the outer side is helical, the end of the hose can be screwed by the helical profiling into an associated internally threaded section of the hose mounting member, wherein the electrically conductive thread is clamped between the profiling and the internally threaded section with formation of an electrical contact.

Such an embodiment advantageously allows “refitting” of a defective hose such as can be desired, for example, by professional users, in that the hose mounting member is unscrewed from the defective hose, the defective or leaking hose section is cut off and the hose mounting member is then screwed back onto the appropriately shortened hose. A further advantage of this variant is that, in the event of repair of the hose, re-establishing contact of the electrically conductive thread with the hose mounting member takes place in particularly simple manner as a consequence of the mentioned clamping of the electrically conductive thread between the profiling of the hose and the internally threaded section.

If such a repair possibility of the hose is not required or, for example, in order to reduce production costs is not desired, in the other variant the end of the hose can be plugged into an associated receiving section of the hose mounting member and glued to the hose mounting member by an electrically conductive adhesive, into which the electrically conductive thread extends with formation of an electrical contact. It is obviously also possible to realize the two variants at the ends of one and the same hose if the hose is to be equipped with not just hose mounting members of one variant.

In principle, the basic hose can be formed by, for example, blow-molding of a suitable plastics material, optionally also with an electrically conductive track wound around the hose in a subsequent step. Thereagainst, however, it is preferred if the wall of the hose is formed overall from a helically wound profile, with adjacent windings of the profile being connected together in media-tight manner. Advantages of such a wound hose by comparison with a blow-molded hose consist particularly in that the hose can be formed with a substantially smooth inner surface and accordingly small flow losses as well as only mild noise output in operation and in addition higher levels of suction performance can be realized as a consequence of good shape stability and restoring capability of the hose.

In a preferred embodiment of the wound hose the adjacent windings of the profile are connected together by a hot-melt adhesive in media-tight manner. This ensures production of the basic hose in a manner which is reliable in terms of process, rapid and economic. However, other possibilities of connection, for example, production of a material couple between the individual profile windings by laser welding, are also conceivable.

With respect to the method, the present invention provides a method for producing a flexible hose, which comprises at least the following three method steps a) to c): a) forming a basic hose having a wall which by an inner side delimits a cavity about a longitudinal axis and has at least at an outer side a profiling which as seen in section has a wave shape with elevations and depressions, wherein the wall is formed from an electrically conductive material or at least one electrically conductive track is formed at the outer side of the wall so that the electrically conductive track extends around the wall; b) applying at least one electrically conductive thread to the outer side of the wall so that the electrically conductive thread extends substantially along the longitudinal axis and transversely to the electrically conductive track; and c) securing the electrically conductive thread to the outer side of the wall so that the electrically conductive thread electrically contacts the electrically conductive track.

Of significance here is the separation of the method steps a) of forming the basic hose on the one hand and b) of applying and c) securing the electrically conductive thread to the outer side of the wall on the other hand. In the result, this leads to the afore-described recycling advantages, because the electrically conductive thread subsequently applied/secured to the outer side of the wall can fundamentally be more easily removed again than a conductor which is an integral constituent of the basic hose.

This separation of the method steps a) on the one hand and b) and c) on the other hand, however, also offers the advantage that in the manner of a construction kit system a hose of the same basic type—which indeed has the electrically conductive track, but (still) has no increased electrical dissipation capability—can, depending on the respective electrical dissipation requirements, be further enhanced by application/securing the electrically conductive thread or even not so enhanced if this is not necessary or desired. Thus, it is also possible to further electrically equip a hose of the same basic type selectively in correspondence with the respective requirements or wishes by the application/securing of different electrically conductive threads which, for example, differ in kind, material, dimensions and/or number.

As already mentioned further above, in step a) of forming the basic hose use can, in principle, be made of a blow-molding process. On the other hand, particularly with respect to simplest possible integration of the electrically conductive track in the hose, it is, however, preferred if in the step a) of forming the basic hose initially a profile of an electrically conductive plastics material is extruded or a profile of two plastics materials of different electrical conductivity is co-extruded so that the profile comprises at least one electrically conductive track, whereupon the profile is helically wound for formation of the wall of the basic hose, in which case adjacent windings of the profile are connected together in media-tight manner. In that regard, for preference the adjacent windings of the profile are, in a manner which is particularly reliable in terms of process, media-tightly connected together by a hot-melt adhesive.

In addition, steps b) of applying and c) of securing the electrically conductive thread to the outer side of the wall can in principle be performed in succession, particularly when the electrically conductive thread and the fastening member for it are two distinct components of the hose. Thereagainst, especially with respect to the most rapid and efficient production possible, it is, however, preferred if the steps b) of applying and c) of securing the electrically conductive thread to the outer side of the wall are performed at the same time, even when the electrically conductive thread and the fastening member for it are two distinct components of the hose.

After execution of the steps a) to c) the hose is already present as a semi-finished plastics material product which in a given case can be supplied as a roll product for further making up, for example, at the manufacturer of terminal equipment such as a vacuum cleaner. The preferred further making-up of the hose can, however, also take place at the hose manufacturer, for example directly subsequent to the production of the semi-finished plastics material product in that after step c) of securing the electrically conductive thread to the outer side of the wall a hose mounting member of an electrically conductive material, which electrically contacts the electrically conductive thread, is attached to one or both of the mutually remote ends of the hose cut to length.

With respect to the device, according to the invention a device for applying an electrically conductive thread to an outer side of a flexible hose is proposed, which has thereat, i.e. at an outer side, a profiling which as seen in section along a longitudinal axis of the hose has a wave shape with elevations and depressions, with the feature that an applicator for the electrically conductive thread is provided and has a rotatable applicator wheel similar to a stock wheel or cell wheel, to the outer circumference of which applicator wheel the electrically conductive thread can be fed and which applicator wheel is adapted to enter into interlocking engagement with the profiling of the hose layable in a hose support so that when the applicator wheel is rotating a relative advance movement between the hose and applicator takes place, in which the applicator wheel applies the electrically conductive thread to the profiling of the hose along the longitudinal axis of the hose while following the elevations and depressions.

Through the embodiment of the applicator wheel in accordance with the invention, which is capable of meshing with the profiling at the outer side of the hose in the manner of a rack drive, there advantageously results a constrained coupling of advance movement and coating/application movement for the electrically conductive thread. As a result, on the one hand it can be ensured that an appropriate or associated length of electrically conductive thread is always deposited or applied per length of hose, which can be conducive particularly to uniform and/or stress-free application of the electrically conductive thread to the profiling of the hose.

On the other hand, it is possible to advantageously use only one drive in order to generate both movements, i.e. relative advance movement for the hose and coating or application movement for the electrically conductive thread. Thus, for example, it is possible for the applicator to be—actively—moved with respect to the hose or the hose to be—actively—moved with respect to the applicator (relative advance), whilst the applicator wheel as a consequence of the interlocking engagement with the hose—passively—rolls thereon and lays down the electrically conductive thread (coating or depositing). In addition, it is possible to fix the applicator and to—actively—rotationally drive the applicator wheel (coating or depositing of the electrically conductive thread), wherein the hose as a consequence of the interlocking engagement between the applicator wheel and the profiling of the hose is—passively—drawn away under the applicator wheel (relative advance). Moreover, there is the possibility of designing the applicator to be movable and to—actively—rotationally drive the applicator wheel (coating or depositing of the electrically conductive thread) so that the applicator together with the applicator wheel by virtue of the interlock between the applicator wheel and the profiling of the hose—passively—moves with respect to the optionally suitably fixed hose (relative advance).

If at least two drives respectively associated with the applicator, the applicator wheel or the hose are provided, then it is possible in addition to co-ordinate the generated movements with respect to movement execution (speed, acceleration) with, for example, use of a suitable electronic system, for example to deposit or attach the electrically conductive thread on or to the profiling of the hose with little tension or, especially, “loosely”, thus relieved of tension.

One of the criteria with regard to which components or subassemblies of the device are constructed or arranged to be stationary and which are constructed or arranged to be movable is the length of the flexible hose to be provided with the electrically conductive thread. In the case of a hose as a roll product or in endless production it is possible, for example, to construct the applicator to be stationary and thereagainst to move the hose with respect to the applicator. Particularly with respect to simple realization of the application process with hoses of defined length a construction of the device is currently preferred in which the hose rest is mounted in stationary position on a frame of the device, wherein the applicator comprises an applicator carriage which carries the applicator wheel and is guided at the frame to be displaceable along the hose rest.

Moreover, with respect to reliable process performance it is also preferred if the applicator wheel is drivably connected with a rotary drive so that the applicator wheel can be actively rotationally driven.

Moreover, an embodiment of the device is preferred in which the applicator comprises an applicator arm on which the applicator wheel is rotatably mounted and which is pivotable with respect to the hose rest about a selectively fixable pivot axis. It is thus possible to use the device with its applicator, without significant conversion work, for hoses of different thickness and/or basic shape (for example cylindrical or conical at the outer circumference). In the case of, for example, conical hoses the applicator wheel can thus follow without problems the thickness of the hose increasing and decreasing over the length of the hose. Through fixing the pivot axis for the applicator arm it is in addition possible to advantageously generate and set a specific pressing pressure of the applicator wheel against the hose in the case of, for example, a hose, which is cylindrical at the outer circumference, with use of the intrinsic elasticity of the hose.

Furthermore, the arrangement is preferably such that the applicator arm together with the applicator wheel and the pivot axis thereof is so positioned with respect to the hose rest that a torque about the pivot axis in the direction of the hose rest results and/or that the applicator arm is resiliently biased about its pivot axis in the direction of the hose rest. The intrinsic weight of the applicator arm together with the components mounted thereon or the center of gravity thereof with respect to the pivot axis and/or the spring force acting on the applicator arm can be so provided or selected in simple manner in the case of such an embodiment that the applicator wheel on application of the electrically conductive thread to the hose always bears against the hose by a defined pressing force.

As already mentioned in the introduction, it is in principle possible to initially position the electrically conductive thread at or in the profiling of the hose by the applicator wheel and secure it to the hose only in a succeeding step, so that the electrically conductive thread is in permanent electrical contact with the electrically conductive track of the hose. Particularly with respect to a largest possible throughput and a high level of process reliability in hose production it is, however, preferred if the application and the securing of the electrically conductive thread to the hose take place at the same time. For this purpose an embodiment of the device is currently preferred in which the applicator comprises a feed device for the electrically conductive thread and a feed device for an adhesive strip, wherein the electrically conductive thread and the adhesive strip can be fed from the feed devices to a pair of guide rollers which are adapted to combine thread and adhesive strip before onward guidance to the applicator wheel takes place. It can thus be ensured on the one hand in simple manner that the electrically conductive thread experiences precise positioning and good securing to the hose and on the other hand that the electrically conductive thread can thus be protected, during application, by the adhesive strip against, for example, excessive tension.

Finally, it is preferred if the applicator wheel has between two hub sections a plurality of axle pins which are uniformly distributed over the circumference and which each rotatably mount a hollow-cylindrical sleeve as pressing body for the electrically conductive thread. During application and securing of the electrically conductive thread to the hose this measure is also advantageously conducive to mechanical load relief of the electrically conductive thread.

Further features, characteristics and advantages of the electrically dissipative flexible hose according to the invention, the method according to the invention for production of such a hose and the device according to the invention for application of an electrically conductive thread to a profiled outer side of a flexible hose are evident to the expert from the following description of preferred embodiments.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A vacuum cleaner hose, as an example of a flexible hose, is denoted generally by the reference numeral10in the figures. According to, in particular,FIGS.2to5or16and17the hose10has a wall12which by an inner side14bounds a cavity16for the conveying of media. At an outer side, the wall12has a profiling20which as seen in section along a longitudinal axis22of the hose10has a wave shape with elevations24and depressions26. As can be best seen inFIGS.3to6and17, provided at the outer side18of the wall12is at least one electrically conductive track28which extends around the wall12and serves the purpose of collecting and passing on electrostatic charges. As explained in more detail in the following, the electrically conductive track28is in electrical contact with at least one electrically conductive thread30, which electrically connects mutually remote ends32,34of the hose10so as to conduct away the electrostatic charges thereat.

In that regard, according to, for example,FIG.6the electrically conductive thread30extends substantially along the longitudinal axis22of the hose10and transversely to the electrically conductive track28or crossing the latter, wherein the electrically conductive thread30is secured to the outer side18of the wall12as can be seen in, in particular,FIGS.3to5and17. In this embodiment, the electrically conductive thread30follows the elevations24and depressions26of the profiling20, wherein the thread30directly bears against the elevations24and—for producing an electrical contact—obviously against the electrically conductive track28, whereas the thread30in the region of the depressions26has a certain spacing from the wall12. By comparison with an equally possible “stretched out” course of the electrically conductive thread30it is thus possible, for example, to achieve a greater degree of flexibility of the hose10.

In the illustrated embodiments the hose is a wound flexible hose10, i.e. a hose10of which the wall12is formed from a profile26helically wound around the longitudinal axis22, wherein adjacent windings of the profile36are connected together to be sealed relative to media. The profile36shown here by way of example has as seen in cross-section two regions, namely a region on the right in each ofFIGS.3to5and17, the cross-section of which has substantially the form of the letter U in “angular” style of writing and which at the wound hose10forms the depressions26of the profiling20, and a region on the left in each ofFIGS.3to5and17, which as considered in cross-section has substantially the form of a letter C in horizontal position or tipped in clockwise sense through 90° and forms at the wound hose10the elevations24of the profile20. As can be readily seen inFIGS.3to5and17, the C-shaped region of a winding of the profile36is quasi “hooked” over the righthand limb of the U-shaped region of an adjacent winding of the profile36so that in each instance a short profile overlap along the longitudinal axis22arises thereat. In order to provide media-tight connection of the adjacent windings of the profile36there is provided in the region of this profile overlap, for example, a hot-melt adhesive38which forms the helically encircling seam shown inFIGS.3to5and17.

It is also evident fromFIGS.3to5and17that the electrically conductive track28of the hose10is formed on the outer side18of the wall12near to or at the elevations24of the profiling20and, in particular, as a sub-region of the profile36, which in the wound state of the profile36similarly extends helically around the longitudinal axis22.

In the illustrated embodiments the profile36is co-extruded from two plastics materials of different electrical conductivity so that the profile36includes the electrically conductive track28. In that regard, a principal part of the profile36can consist of a non-conductive plastics material such as, for example, polyethylene (PE), polypropylene (PP) or an ethylene vinyl acetate copolymer (EVAC), whereas the electrically conductive track28is formed from a conductive plastics material. The latter can be, for example, a PE, PP or EVAC basic material which is rendered conductive by addition of conductive components such as, for example, carbon particles.

However, in the alternative it is also possible in correspondence with the respective electrical dissipation requirements to co-extrude the profile36entirely from such electrically conductive plastics materials and, in a given case, to even extrude with material uniformity. In such a case the profile overall forms the electrically conductive track by its outer surface.

As far as the hot-melt adhesive38is concerned this can similarly consist of a plastics material such as, for example, PE or EVAC, which is either non-conductive or is made conductive.

By the term “electrically conductive thread”30generally used here there is to be understood on the one hand a metalized thread, cord or yarn, for example an elastic yarn of a plastics material such as polyamide (PA), which is provided with, for example, a silver coating or a coating of copper, gold or platinum promising very good conductivity, or, however, a track or a (adhesive) strip of a plastics material or synthetic resin made electrically conductive in suitable manner, but also on the other hand pure metallic conductors such as wires or strands of copper or the like, wherein the actual realization of the electrically conductive thread30depends on which demands are placed on the hose10with respect to, in particular, the electrical and mechanical properties thereof. Thus, for example, in the case of a flexible hose10which is subject in use to greater degrees of alternating bending loads or tension loads it has to be ensured that the electrically conductive thread30does not break or tear or do so prematurely, which tends to exclude metallic conductors, which may be liable to work-harden, from such a case of use. With respect to electrical conductivity, a specification with respect thereto can be, for example, that the entire hose has to have only a predetermined resistive impedance able to be achieved, for example, by suitable selection of the electrically conductive thread30.

As already mentioned further above, at least one electrically conductive thread30is provided, i.e. in correspondence with the respective requirements it is also possible to provide several electrically conductive threads in order to, for example, reduce the electrical resistance in an overall arrangement and/or provide a—optionally multiple—redundant overall arrangement. In that regard, the electrically conductive threads30can run adjacent to one another or at least partly cross or intersect under electrical contact with one another. In such a case the electrical connection of the mutually remote ends32,34of the hose10and the electrical contacting of the electrically conducting track28is achieved by the overall arrangement of electrically conductive threads30. In other words, it is in principle possible that none of the electrically conductive threads30of such an overall arrangement by itself bridges the entire path between the mutually remote ends32,34of the hose10, but the overall arrangement and/or only a part or one of the electrically conductive threads30of such an overall arrangement contacts the electrically conductive track28.

As, moreover,FIGS.3to6and17, in particular, show, the at least one electrically conductive thread30in the illustrated embodiments is secured to the outer side18of the wall12by an adhesive strip40. According toFIG.6the adhesive strip40can in that case cover the electrically conductive thread30to both sides as seen in circumferential direction of the hose10. The adhesive strip40is then designed so that its adhesive side reliably adheres to the plastics material of the wall12or of the profile36. Possible backings for the adhesive strip40are foils, non-woven fabrics or textiles of a synthetic material such as, for example, PE, PP, polyvinylchloride (PVC), polyethylene terephthalate (PET), polyimide (PI) or polyurethane (PUR), according to the respective field of use of the hose10.

In the embodiment according toFIGS.15to17there is an additional feature that the adhesive strip40covering the electrically conductive thread30is surrounded at the outer side18of the wall12of the hose10by a braiding42. The braiding42can consist of monofilamentary and/or multifilamentary threads of a thermoplastic plastics material such as, for example, PA or PE. The multifilamentary threads during bending of the hose10lay flatly against the hose10on the tension side and compress on the compression side of the hose10transversely to the thread and thus also towards the wall12of the hose10, so that the braiding42always bears against the wall12. In a particularly advantageous mixture ratio of 50% multifilamentary threads to 50% monofilamentary threads the braided surface of the hose10in addition always remains closed. The electrically conductive thread in an embodiment, which is not illustrated here, can thus be held in position at the wall by the braiding even without the adhesive strip covering it, wherein in fact through suitable placing of the electrically conductive track at the elevations of the profiling it is ensured that the electrically conductive thread crosses the electrically conductive track under contact and thus makes electrical contact.

The afore-described hose10can in principle be produced as a roll product at the hose manufacturer and, for example, be supplied to the manufacturer of relevant terminal equipment such as, for example, vacuum cleaners, where further making-up of the hose10is then carried out, which usually comprises cutting the hose10to length and providing the hose10at the ends with use-specific end members. However, it is also possible—and frequently the case—that the hose manufacturer further makes up the hose10.

In the embodiment inFIGS.1and2the hose10is cut to length and provided at the two mutually remote ends32,34with a hose mounting member44,46of an electrically conductive material, by way of which a desired conducting away of electrostatic charges to, for example, terminal equipment and the grounding thereof can take place. Two different forms of hose mounting members44,46are illustrated by way of example at one and the same hose10inFIGS.1,2,4and5. These hose mounting members44,46can optionally be connected or provided with a further use-specific end piece (not shown) so as to provide, for example, a connection geometry adapted to the specific use, but often also so as to provide a possibility of relative rotation between hose mounting member and end piece. Such hose mounting members and end pieces are familiar to the expert so that there shall be only brief discussion in the following of how the respective hose mounting member44,46is secured to the wall12of the hose10and in that case an electrical contact between the electrically conductive thread30and the respective hose mounting member44,46is effected.

In the hose mounting member44, which is on the left inFIGS.1and2and the outer-side profiling20of which is helical as previously described, of the hose10the end32of the hose10is screwed together with the helical profile20in an associated internally threaded section48of the annular hose mounting member44. A screw connection of that kind—which is reversible—has the advantage that in the case of, for example, a damaged hose10the hose mounting member44can be unscrewed, the hose10can be newly cut to length with removal of the defective hose region and then newly made up to finished state without problems by screwing back on the hose mounting member44. In this form of securing, the electrically conductive thread30is clamped between the profiling20and the internally threaded section48with formation of an electrical contact. This is illustrated by way of example on the left inFIG.4, where an end49, which projects beyond the adhesive strip40, of the electrically conductive thread30undergoes clamping of that kind.

On the other hand, in the case of the hose mounting member46, which is on the right inFIGS.1and2, of the hose10the end34of the hose10is plugged into an associated—here substantially hollow-cylindrical—receiving section50of the annular hose mounting member46and glued to the hose mounting member46by an electrically conductive adhesive52. As indicated inFIG.5on the right by a dashed line, the electrically conductive thread30extends by an end53, which protrudes beyond the adhesive strip40, into the electrically conductive adhesive52with formation of an electrical contact.

A method of producing the flexible hose10sofar as described comprises in general the following three method steps a) to c): In a first step a), formation is carried out of a basic hose comprising the wall12which by its inner side14delimits the cavity16about the longitudinal axis22and has at least at its outer side19the profiling20which as seen in section has the wave shape with elevations24and depressions26, wherein the wall12in its entirety is formed from an electrically conductive material or at least the electrically conductive track28at the outer side18of the wall12, so that the electrically conductive track28extends around the wall12. The basic hose produced to that extent is in principle already capable of use, i.e. no specific requirements with respect to the capability of dissipating electrostatic charges are imposed thereon, thus this basic hose can already be made up by cutting to length and providing it with suitable end pieces.

Only in a following step b) is the application now carried out, in the case of higher demands on the hose10with respect to capability of conducting away electrostatic charges, of the at least one electrically conductive thread30to the outer side18of the wall12, so that the electrically conductive thread30extends substantially along the longitudinal axis22and transversely to the electrically conductive track28. In other words, in this step the encircling electrically conductive track28is short-circuited or at least prepared for that purpose by the electrically conductive thread30.

In order, finally, to maintain this electrical state in further processing and in later use of the hose10or bring about that state for that purpose, securing of the at least one electrically conductive thread30to the outer side18of the wall12is carried out in a further step c) so that the electrically conductive thread30—permanently—electrically contacts the electrically conductive track28. This securing can, as already mentioned above, be effected by attaching or applying the adhesive strip40and/or the braiding42to the outer side18of the wall12of the hose10.

Preferred sub-steps of the step a) of forming the basic hose comprise, as already similarly discussed above, initially a sub-step in which the profile36is extruded from an electrically conductive plastics material or co-extruded from two plastics materials of different electrical conductivity so that the profile36has at least the electrically conductive track28even if not fully electrically conductive. In a further sub-step the profile36is thereupon helically wound for formation of the wall12of the basic hose, wherein adjacent windings of the profile36are media-tightly connected together by, for example, the hot-melt adhesive38, as is known per se.

With respect to rapid and efficient mass production of hoses10it is particularly preferred if the steps b) of applying and c) of securing the electrically conductive thread30to the outer side18of the wall12are performed at the same time. A device which can be used for that purpose is described further below.

Finally, after the step c) of securing the electrically conductive thread30to the outer side18of the wall12the afore-described hose mounting member44,46of an electrically conductive material can, for example, be attached to one or both of the mutually remote ends32,34of the hose10, which is cut to length as desired or necessary, and electrically contacts the electrically conductive thread30.

Details of a device54for application of an electrically conductive thread30(or several electrically conductive threads30) to the outer side18of, for example, the afore-described flexible hose10, can be inferred fromFIGS.7to14. The device54has a frame56, which in the illustrated embodiment is assembled from aluminum sections and at which the individual components or subassemblies of the device54are arranged. AsFIGS.7to9, in particular, show, the frame56is constructed in the manner of a ladder frame with two longitudinal profile members58fixedly connected together by a plurality of transverse profile members60.

A hose rest64consisting of an elongate angle profile member with a V-shaped cross-section is erected on the transverse profile members60of the frame56—see, in particular,FIGS.7and8on the lefthand side andFIG.9on the righthand side—by way of mounting profile members62, the angle profile member being secured to the mounting profile members62by way of securing straps66. AsFIGS.7to13show, the hose support64serves for reception of the hose10, which is to be equipped with the electrically conductive thread30and which automatically moves into a stable, lower end position in the hose support64by virtue of the V-shape of the hose support64.

A core component of the device34is an applicator68for the electrically conductive thread30, which—as described in more detail in the following—has a rotatable applicator wheel70similar to a stock wheel or cell wheel (seeFIGS.10and12to14), the electrically conductive thread30being fed to the outer circumference of the applicator wheel and the applicator wheel being adapted to enter into interlocking engagement with the profiling20of the hose laid in the hose support64. As a result, when rotation of the applicator wheel takes place there is a relative advance movement between hose10and applicator68in which the applicator wheel70applies the electrically conductive thread30to the profiling20of the hose10along the longitudinal axis22of the hose10while following the elevations24and depressions26.

In the illustrated embodiment the arrangement is such that the hose support64is mounted in stationary position at the frame56, whereas the applicator68comprises an applicator carriage72which carries the applicator wheel70in a manner still to be described and—as can be clearly seen in a comparison ofFIGS.7to9—is guided at the frame56to be displaceable along the hose support64(cf. also the double arrow74for the longitudinal movement inFIGS.10,11and14). For that purpose, the longitudinal profile members58of the frame56are each provided at the upper side thereof with a respective continuous guide groove76in which on each side of the frame56a pair of profile sliders78engage to be capable of sliding, the sliders for their part being fixedly connected with the applicator carriage72. The applicator carriage72itself is, in the illustrated embodiment according to, in particular,FIGS.10to14, again assembled from a plurality of aluminum profile sections, of which one profile section extends as cross member80over the hose support64.

The applicator68further comprises an applicator arm82, on which the applicator wheel70is rotatably mounted in a manner still to be described and which is pivotable with respect to the hose support68about a selectively definable pivot axis84, which can be best seen inFIGS.11and14(cf. also the double arrow86for the pivot movement in these figures). For that purpose, the applicator arm82is pivotably coupled to the cross member of the applicator carriage72with the assistance of a joint88with a clamping lever90. If the clamping lever90is fixed, then the applicator arm82is fixed in its respective angular position about the pivot axis84. Thereagainst, when the clamping lever90is released, the applicator arm82can pivot about the pivot axis84.

According toFIG.14the pivot axis84and the applicator wheel70are disposed at mutually remote ends of the applicator arm82. As can be further seen particularly inFIGS.10and14, the applicator arm82together with the applicator wheel70and its pivot axis84is so arranged with respect to the hose support64that a torque about the pivot axis84in the direction of the hose support64results and, in particular, due to the intrinsic weight of the applicator arm82and the components or subassemblies mounted thereon. As a consequence of this torque the applicator wheel70is pressed against a hose10, which is placed in or at the hose support64, and kept in engagement with the profiling20thereof.

If need be, the applicator arm82can also be manually pushed in the direction of the hose10and then fixed in this pressing position by fixing the clamping lever90. In a variant, which is not illustrated in the figures, the applicator arm82can in addition also be resiliently biased about its pivot axis84in the direction of the hose support64, for example by a tension spring, which is arranged to be effective in terms of actuation between the applicator arm82and lower part of the applicator carriage72.

It will be evident to the expert that by these measures the applicator wheel70can be reliably held in engagement with the profiling20of the hose10resting on the hose support64. In that case, hoses10with different diameters and shapes (for example substantially cylindrical or conical) can be processed, i.e. provided with an electrically conductive thread30.

As, moreover, can be best inferred fromFIGS.10,11and14, the applicator arm82has a head part92consisting of an aluminum profile section, on which further components or subassemblies of the applicator68are mounted as described in the following. These components and subassemblies are in detail a feed device94for the electrically conductive thread30, a feed device96for the adhesive strip40, a guide roller arrangement96with a pair of guide rollers100,102for combining the electrically conductive thread30with the adhesive strip40before transfer to the applicator wheel70takes place, and a mounting and drive arrangement104for the applicator wheel70.

According toFIGS.10,11and14initially the guide roller arrangement98is mounted by a mounting profile section106at the top on the head part92of the applicator arm82so that the guide rollers100,102are disposed above the applicator wheel70in a position aligned with respect to the applicator wheel70, as can be clearly seen inFIGS.12and13. The guide rollers100,102are in that case rotatably mounted in cantilever manner on the mounting profile section106in a suitable way.

In addition, a roll holder108, at the free end of which an adhesive strip roll110is rotatably mounted and, in particular, similarly in cantilever manner, of the feed device96is mounted on the side of the head part92and the mounting profile section106remote from the pivot axis84. According to, in particular,FIGS.12and13the adhesive strip roll110, which is arranged with the axis of rotation thereof above the guide roller arrangement98, is similarly disposed in alignment with the guide rollers100,102.

Moreover, a spool holder112, which in the illustrated embodiment carries four spools114with electrically conductive threads30, the spools being rotatably plugged onto parallel axle pins (not illustrated), of the feed device94is mounted at the top on the mounting profile section106. A fastening angle member116for an end of a hose118, the other end of which is secured by a bracket120laterally to the mounting profile section106, is mounted on the end of the spool holder112remote from the adhesive strip roll110. Finally, this bracket120also holds a tubelet122for the feed, more precisely guidance of the electrically conductive threads30to the guide roller arrangement98.

In this respect it is apparent that the adhesive strip40can be unrolled from the adhesive strip roll110of the feed device96and fed to the guide roller arrangement98. At the same time electrically conductive threads30can be unspooled from the spools114, collected by way of the hose118and—guided through the tubelet122—fed to the guide roller arrangement98, where the electrically conductive threads30are combined with the adhesive strip40.

Moreover, a mounting block124of the mounting and drive arrangement104for the applicator wheel70is mounted below the head part92of the applicator arm82. In the illustrated embodiment the mounting block124is of two-part construction, with a part which is on the left inFIG.13and in which a drive shaft126for the applicator wheel70is rotatably mounted by way of two roller bearings, and a part which is on the right inFIG.13and on which an axle pin128for mounting of the applicator wheel70is mounted by way of a roller bearing at the wheel side. In addition, a preferably electrically rotary drive132, which is in driving connection with the applicator wheel70by way of the drive shaft126, is flange-mounted on the side, which is at the left inFIGS.12and13, of the mounting block124by way of a mounting flange130.

Finally, further details with respect to the applicator wheel70can be inferred fromFIGS.10and12to14. Accordingly, the applicator wheel70has between two hub sections134,136a plurality—in the illustrated embodiment five (seeFIG.14)—of axle pins138uniformly distributed over the circumference. The axle pins138each rotatably mount a respective hollow-cylindrical sleeve140as pressing body for the electrically conductive thread30. It can also be inferred fromFIG.13that the hub section134, which is at the left in this figure, of the applicator wheel70is connected with the drive shaft126in the manner of a coupling to be secure against relative rotation, whereas the hub section136, which is on the right in this figure, of the applicator wheel70receives the roller bearing which co-operates with the axle pin128in the mounting block124of the applicator wheel to provide rotational mounting.

As, in particular,FIGS.10and14show, the adhesive strip40combined with the electrically conductive threads30is guided, starting from the guide roller arrangement98, through a slot-like cut-out142in the head part92of the applicator arm82and in the mounting block124, which is mounted thereon, to the applicator wheel70, by way of which the electrically conductive threads30are applied and secured under the adhesive strip40to the outer side18of the hose10. In that case the applicator wheel70, the sleeves140of which engage in interlocking manner with the profiling20of the hose10, roll along on the hose10.

It will be apparent that through driving the applicator wheel70by the rotary drive132not only the electrically contacting application and securing of the electrically conductive threads30to the hose10thus take place, but also the advance movement between the applicator68and the hose10, which rests on the hose support64, is generated, in which the applicator carriage72as shown inFIGS.7to9moves over the hose support64fixed at the frame56. At the end, the hose10, the electrically conductive track28of which is through-plated or short-circuited by way of the applied electrically conductive threads30, can be removed from the hose support64by the device54before the further making-up of the hose10is carried out by possible further cutting of the hose to length and attachment of the hose mounting members44,46.

A flexible hose, particularly vacuum cleaner hose, has a wall which by an inner side delimits a cavity for the conveying of media and has at least at an outer side a profiling which as seen in section along a longitudinal axis of the hose has elevations and depressions. At least one electrically conductive track, which extends around the wall and is in electrically contact with at least one electrically conductive thread which electrically connects mutually remote ends of the hose, is provided at the outer side of the wall. The electrically conductive thread, which extends substantially along the longitudinal axis of the hose and transversely to the electrically conductive track, is secured to the outer side of the wall, whereby the hose in the case of use of a comparatively small amount of electrically conductive materials has improved suitability for recycling. In addition, a method for producing such a hose and a device usable for that purpose are proposed.

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