Patent Description:
The flexible shaft according to the invention is suitable for transmitting a torsion force in many applications, particularly when used inside a casing tube. In particular, this case discloses an air-conditioning cleaning device, which is known from, among others, Finnish patents <NUM> and <NUM> and from utility model <NUM>. In the device for cleaning air-conditioning ducts, a flexible shaft is used to rotate a cleaning brush. The brush device used in the solution comprises a motor-driven brush, which is supported on the wall of the duct with the aid of a carrier brush. The flexible operating arm comprises a casing tube and a braided steel cable fitted inside it. The flexible shaft is rigidly attached from the casing tube to the body of the drive motor. The drive shaft is rigidly joined to the shaft of the motor, so that torque is efficiently transmitted in the long, flexible shaft to the brush head. During cleaning, the brush head is operated in both directions.

A steel cable of this kind can be wound to either the right or the left. Its torque-transmitting capability is therefore not symmetrical. A second drawback with this known solution is that the steel cable is heavy, with the reel weighing as much as several tens of kilogrammes. Document <CIT> presents a torsion shaft having a glass fibre core and a plurality of left- and right-hand wrapped helixes of single strands and a hard adhesive interposed between the fibre strands for bonding strands together.

The applicant's <CIT> (falling within the terms of Art. <NUM>(<NUM>) EPC) presents a flexible torsion shaft, where a core element and a reinforcement comprising a polymeric base substance and a multi-layered reinforcing-fibre reinforcement. Each reinforcing-fibre layer is wound around the core element by hoop winding using a wide range of angles. There is in at least one reinforcing-fibre layer a reinforcing-fibre reinforcement wound alternate in an opposite direction. The document teaches to increase the winding angle as the average layer diameter increases and to take several reinforcing-fibre layers into the same impregnation polymeric base substance, which is absorbing the entire layer.

Specifically, this document teaches to use epoxy as polymer base substance, but in the outmost layer polyurethane can be used. In the flexible torsion shafts the winding angles vary <NUM>° - <NUM>°, and even up to <NUM>°.

The present invention is intended to present a high-powered flexible torsion shaft exploiting the great tensile strength of fibre without cutting the structure open.

Flexible composite torsion shaft (<NUM>) is intended to be attached to a drive shaft, and having a core element (<NUM>, <NUM>') and a reinforcement comprising a polymeric base substance (<NUM>, <NUM>') and a multi-layer (<NUM>, <NUM>', <NUM>'', <NUM>‴) reinforcing-fibre reinforcement, with each reinforcing fibre layer being wound around the core element (<NUM>) by hoop-winding, according to independent claim <NUM>.

The reinforcing fibre layer thus comprises one winding layer at a selected angle. In addition, on the torsion shaft or within optional casing tube there is preferably a PTFE coating, preferably a Xylan <NUM> PTFE coating (Teflon®). This significantly reduces friction.

The torsion shaft according to the invention is characterized by being the polymeric base substance (<NUM>, <NUM>') is polyurethane-based polymer and said increasing winding angles are in the range of <NUM> - <NUM> degrees.

The device according to the invention for cleaning air-conditioning ducts comprises reeling means fitted to the casing tube for the flexible torsion shaft, a drive-motor mechanism for rotating the flexible torsion shaft, and a brush device attached to the free end of the flexible torsion shaft, in which the flexible torsion shaft and the casing tube are according to what is described above.

In the manufacturing stage, polymer is fed from consecutive extruders, but the polymer finally forms a network, homogenously combining all the feed layers.

The solution according to the invention has the advantage that the cross-braided composite cable has very great torsion-strength symmetrical torque properties relative to its weight. It is also considerably lighter than a steel cable. These advantages make the torsion shaft, and through it the entire cleaning device, more user-friendly. Naturally, symmetricity can be deviated from by winding a chosen amount more in a chosen direction than in the opposite direction.

A polyurethane-based polymer and a winding angle of <NUM> - <NUM> degrees are used to create a high-powered and flexible torsion shaft. Further, in an improved embodiment a polymer is used, which has a great elongation and tensile strength. The great elongation and tensile strength make it possible to exploit the great tensile strength of the fibre without the fibre cutting the structure open.

The body of the torsion shaft is preferably of epoxy and the reinforcing fibres are mainly of glass fibre. Polyamide (Nylon®), aramid (Kevlar®), UHMWPE (Dyneema ®), and carbon fibre can also be used for this purpose. The flexible torsion shaft is preferably manufactured by means of pultrusion, in which filament fibres are wound around a preform. Some type of standard filament winder machine can be used. The fibres to be wound around the core wire are soaked in resin and a layer of a chosen thickness is hardened in an oven. The machine winds each layer in two directions, so that by pulling backwards and forwards the winding angles are in opposite directions and the torsion shaft is naturally given symmetrical properties.

According to the invention, the desired strength and stiffness properties are achieved by winding several layers around a core wire, preferably at different winding angles. The main rule for the outer layers to be wound at an averagely steeper angle relative to the core wire. The fibres weigh <NUM> - <NUM> % of the total weight.

Steeper winding (e.g., <NUM>°) creates a torsional force (in the outer surface), while a gentler (e.g., <NUM>°) winding angle creates stiffness and tensile strength. The embodiments use suitable combinations to achieve an optimal result. A great torsional force together with flexibility is most easily achieved using urethane combined with a winding angle of <NUM> - <NUM>°).

The casing tube is preferably of polyamide, so that the material hardness and other properties will minimize friction.

The diameter of the flexible torsion shaft is <NUM> - <NUM>, preferably <NUM> - <NUM>. The diameter of the core (wire, cable, or braided cord or rubber, e.g. EPDM) is arranged in such a way that the casing layer has a total thickness of at most <NUM>, preferably at most <NUM>.

In brush cleaning devices, the flexible torsion shaft <NUM> should have a minimum radius of curvature of <NUM> - <NUM>, preferably <NUM> - <NUM>. In other uses, such as in a drill's flexible torsion shaft, the flexibility can be substantially smaller.

In the following, the invention is described in greater detail with the aid of an embodiment example with reference to the accompanying drawings, in which.

The components of the flexible shaft arrangement <NUM> are a casing tube <NUM> and the torsion shaft <NUM> itself. The length of the shaft arrangement can be <NUM> - <NUM> and the diameter of the torsion shaft <NUM><NUM> - <NUM>.

The casing tube <NUM> is typically of polyamide and is intended to protect structures by keeping the rotating torsion shaft <NUM> away from, e.g., the duct structures. Polyamide has a low coefficient of friction with most of the polymers binding the reinforcing fibres, namely polyurethane. A particularly advantageous totality is achieved if the flexible shaft is coated with polytetrafluorethylene, i.e., PTFE (Teflon®). Alternatively, the inner surface <NUM> of the protective tube can be covered with PTFE (<FIG>).

The body of the torsion shaft <NUM> of <FIG> is of epoxy and filament wires <NUM>, <NUM>', generally of glass fibre, are wound on top of it in two directions. In this case, the core is a bunch of fibres <NUM> and a polyethylene membrane <NUM> is on top of it. Unlike in the figure, the bunch of fibres fills the entire space and the resin is impregnated inside the bunch.

The winding angle of the filament wires <NUM>, <NUM>' is critical to the torsional stiffness. In the figures, the winding angle is in the order of <NUM>° (not part of this invention). Preferably it is <NUM> - <NUM>°. A gentle winding angle will make the torsion shaft stiff, leading to a large curvature radius. A large winding angle gives good torsional stiffness. Several layers can be wound at different angles to achieve the desired strength and stiffness properties. The main rule is that the outermost layers are always wound at a steeper angle relative to the core wire. The weight of the fibres is <NUM> - <NUM> % of the total weight. The harder the polymer the steeper the angle at which the last fibre is wound, otherwise the fibre will begin to abrade through the polymer.

The axial filaments <NUM>, which are important in terms of the tensile strength of the shaft, are marked in the figures.

The flexible torsion shaft has a diameter of <NUM> - <NUM>, preferably <NUM> - <NUM>. The length of such shafts is in the range <NUM> - <NUM>. Nominal torque M is in the range <NUM> - <NUM> and the torsional shaft's diameter D is then in the range <MAT>.

It is important to adjust the material hardness of the casing tube, as it determines the magnitude of the friction.

In one embodiment, the core, i.e., the core wire, is a nylon cord, with epoxy cast on top of it and glass-fibre filaments wound on the surface. The fibre bunch, fabric cord, or braided rubber twine used as the core should be isolated, to prevent the epoxy from being absorbed in the core. Either absorption with oil, or a suitable membrane such as polyethylene can be used to achieve this isolation.

According to the invention, multi-layer reinforcing fibre winding is used and, if necessary, at least two different polymer layers, with a hard inner layer and a more elastic polymer outer layer (not part of this invention). One such polymer pair is Axson tech. (FR) EPOLAM <NUM> (hard epoxy) and EPOLAM 8064R (flexible epoxy). Usually, a layer thickness of less than <NUM> does not require a second polymer. The casing layer usually has a thickness of at most <NUM>, preferably at most <NUM>. Experience has shown that a layer thickness greater than <NUM> and generally greater than <NUM> is of no benefit, as then the torsion shaft loses its elasticity. In the surface layer, polyurethane can be used, which has an elasticity many times that of the elastic epoxy referred to above. The problem with epoxy is its poor elongation, which leads to stiffness in the shaft. The same manufacturer's polyurethane resins are 'RE11550 polyol' and 'RE1020-isocyanate', a mixture of which has an elongation value of <NUM> %. In addition to these, hybrid resins are available, with different grades of resin, such as epoxy and urethane resins, being arranged together. The core component is intended to prevent buckling in the casing component when the torsion shaft is bent into a curve. It is obvious that as polymers develop the performance values of the end product will develop further. The diameter of drill shafts can be <NUM> - <NUM>. Shafts with a diameter of <NUM> - <NUM>, for example, are suitable for opening drainpipes.

In the latest embodiments, the core is a flexible, braided cord, which allows the internal diameter of the polymer layer to be increased in step with the external diameter. Thus, for example, in one torsion shaft with a diameter of <NUM> (<FIG>), the rubber core cord <NUM>' (braided) has a diameter of <NUM>. This is topped by a thin (<NUM>) polyethylene film <NUM> to prevent the absorption of epoxy resin (not part of this invention). In the following description the winding angles are out of the scope of the claims, it is to be understood that the winding angles within the scope of the claims are in the range of <NUM>-<NUM> degrees as in appended claim <NUM>; a reinforcing-wire layer <NUM>, with a thickness of <NUM> Tex (glass-fibre), wound at a gentle winding angle of <NUM>°, comes first in the polymer layer <NUM> (thickness <NUM>). Layers of the same reinforcing-wire follow on top of it at a steeper <NUM>° angle, but alternate in different directions, with a layer <NUM>' of glass-fibre, until a total thickness of <NUM> is achieved. A layer <NUM>" of reinforcing-fibre lies in an elastic epoxy layer <NUM>' (thickness <NUM>) at an increasingly steep angle (<NUM>°), <NUM>" until the last layer <NUM>‴ of <NUM>-mm wire is hoop wound at about <NUM>°. About <NUM> reinforcing-fibre layers are made with <NUM>-mm wire (roving), which make a thickness of about <NUM> together with the epoxy resin.

In newer embodiments, the same fibre as in the winding is preferably used as the core, i.e. the centre wire, the centre wire (bunch) beings impregnated with the same resin as the winding layers, because it must have the same heat resistance as them. It is also possible to use, as the centre wire or core cord <NUM>', a round power-transmission belt, in which, for example, there is a polyester thread <NUM>'' and a polyurethane coating (<FIG>).

Reinforcing fibres: glass-fibre, polyamide (Nylon®), aramid (Kevlar®), UHMWPE (Dyneema®), carbon fibre. Rovings to be used <NUM> - <NUM> Tex (glass-fibre bunches), in a circular fibre bunch, thickness <NUM> - <NUM>.

Brush cleaning devices for air-conditioning ducts, of which an example is the device according to utility model FI-U-<NUM>, shown in <FIG>, are a particular application of the flexible torsion shaft. The flexible torsion shaft according to the invention suits nearly all machines designed for a corresponding task, in which the flexible torsion shaft together with the casing tube can be reeled onto a reel of a quite small diameter (<NUM> - <NUM>). The brush cleaning device according to <FIG>, incorporates a disc <NUM>, set to be rotated with the aid of a shaft <NUM>. The circumference of the disc <NUM> has pins <NUM>, between which the flexible torsion shaft <NUM> with a casing tube is reeled. The brush device <NUM> is attached to the flexible shaft in the hub <NUM>. The start of the casing tube <NUM> is permanently attached to the motor assembly's <NUM> body and the torsion shaft <NUM> itself is attached to a rotating toothed-belt gearwheel <NUM>. The rotating force generally comes through the shaft, however the construction of the rotation device does not fall within the scope of the present invention.

The newest embodiments use the following dimensions.

The wall thickness is usually <NUM> ±<NUM> %, if the shaft diameter is <NUM> or greater, and in thinner shafts the wall thickness is usually <NUM>% ±<NUM> % of the shaft diameter.

In winding, a fibre is used, the thickness of which is <NUM> tex - <NUM> tex (±<NUM> %), corresponding to the table's diameter range <NUM> - <NUM>.

Preferred matrix: thermosetting polyurethane prepolymer resin.

Shaft coated with Xylan <NUM> PTFE coating (Teflon®).

In industrial manufacture, either cross-winding machines equipped with up to <NUM>-metre-long back-and-forwards winding devices are available, or else continuously operating pull-winding machines (<FIG>), in which there are a chosen number of consecutive winding devices <NUM>/<NUM>, <NUM>/<NUM>, and extruder units <NUM>,<NUM> for manufacturing a multi-layer shaft. <FIG> shows the principle of such a machine. For continuous drive, a drive rope is needed, which is preferably a round belt commonly used in transmissions, in which there is a centre thread <NUM>'' and a polyurethane coating. For example, an <NUM>-mm Eagle Green <NUM> Reinforced Textured Round by Fenner Drives, Inc. USA, can be used. This provides a tension of <NUM> N at an elongation of <NUM> %.

The core cord <NUM>' can be pulled from a large reel (not shown), which can contain up to several kilometres for continuous production. <FIG> shows two winding pairs <NUM>/<NUM> and <NUM>/<NUM>, but there can be the number of them necessary for the selected layer thickness. In <FIG>, polymer impregnation using extruders <NUM> and correspondingly <NUM>, takes place after two fibre layers, but several reinforcing-fibre layers can be taken into the same impregnation, provided the polymer is absorbed in the entire layer.

Claim 1:
High-powered and flexible composite torsion shaft (<NUM>), which is intended to be attached to a drive shaft, and which torsion shaft (<NUM>) has
• a core element (<NUM>) and a reinforcement comprising a polymeric base substance (<NUM>, <NUM>') and
• a multi-layered (<NUM>, <NUM>', <NUM>", <NUM>"') reinforcing-fibre reinforcement forming a casing layer around the core element, each reinforcing-fibre layer being wound around the core element (<NUM>) by hoop winding, in which in at least one reinforcing-fibre layer (<NUM>, <NUM>', <NUM>", <NUM>‴) there is a reinforcing-fibre reinforcement wound alternate in an opposite direction, and where
• the winding angle is increasing as the average layer diameter increases, and several reinforcing-fibre layers (<NUM>, <NUM>',<NUM>", <NUM>‴) are taken into the same impregnation by polymeric base substance (<NUM>, <NUM>'), which is absorbing the entire layer (<NUM>, <NUM>', <NUM>", <NUM>‴),
• the core element is preventing buckling in the casing component when the torsion shaft is bent into a curve.
• a length of the flexible torsion shaft (<NUM>) is <NUM> - <NUM>,
• the nominal torque M is in the range <NUM> - <NUM> and the diameter D of the torsion shaft is then in the range D = <NUM> x √(M/Nm) ±<NUM>%,
• the minimum curvature radius of the high-powered flexible torsion shaft (<NUM>) is <NUM> - <NUM>, preferably <NUM> - <NUM>, and
• the weight of the fibres is <NUM> - <NUM> % of the total weight,
characterized in that the polymeric base substance (<NUM>, <NUM>') is polyurethane-based polymer and said increasing winding angles are in the range of <NUM> - <NUM> degrees.