Background art In German Utility Model No. 8712161 and in EP-A-0557049, two apparatuses are disclosed for cleaning walls, ceilings and the like, each having an extendable cleaning tool supporting handle. This handle comprises a pair of hollow rigid telescoping tubes, having an inner flexible hose for delivering a liquid to the cleaning apparatus.

This arrangement has the apparent drawback that the hose kinks when the telescopic handle supporting the apparatus is retracted. This may generate folds in the flexible hose, which reduce or obstruct the passage of the feed liquid. In addition, each time that the telescopic handle is retracted or extended, the flexible hose bends or extends. Such operating feature causes a fast wear of the flexible hose and deteriorates its tightness features. Such a behavior is particularly dangerous when the feed liquid like steam has a high temperature, like steam, in which case a liquid leakage may cause damages and injuries to users.

A similar arrangement is disclosed in EP-A-1004263. Here again the cleaning tool supporting handle is made of a pair of telescopically coupled tubes and the fed liquid passes through a flexible hose, which is coiled outside the two tubes.

This embodiment allows to visually inspect the wear conditions and the proper positioning of the flexible hose, even if this latter is still exposed to continuous bending and extension each time the support handle is retracted or extended.

Further, the outside position of the flexible hose may cause a size increase which affects the comfort of use of the whole apparatus.

US-A-4,778, 298 discloses an apparatus for cleaning floors, windows and similar surfaces, which apparatus confuses two or more hollow tubular members. A first tubular member supports a cleaning tool at one longitudinal end and is connected to a second tubular member at the other end. A feeding liquid is conveyed to the cleaning tool by means or two or more operatively connected conduits, each located inside one of the two tubular members.

An apparent drawback of this solution consists in that the overall length of the cleaning device cannot be continuously adjusted, but only by changing the number of sequentially interconnected tubular elements.

FR-A-2676376 discloses an apparatus for cleaning glasses and other flat surfaces, having a telescopic support handle. The support handle comprises two outer tubular members, which are adapted to slide one into the other and contain respective telescoping inner conduits therein, for delivery of cleaning liquid at ambient temperature.

This arrangement makes use of rigid conduits, which are less exposed to fast wear and deterioration than flexible hoses, but has no technical feature suitable to ensure high tightness and insulation properties with high temperature feeding liquids. Particularly, there is no provision for detachable and replaceable inner conduits for better adaptation to different types of feeding liquids, or seal devices operating ad high temperatures and/or pressures.

Summary of the invention A general object of this invention is to obviate the above drawbacks, by providing a cost-effective working tube assembly for delivering working fluids in cleaning apparatus.

A primary object is to provide a tube assembly which may be used with high temperature working fluids.

A particular object is to provide a tube assembly which may be used with various kinds of working fluids.

A further object is to provide a tube assembly which may be easily and safely used, and ensures high working fluid tightness and insulation, thereby preventing dangerous fluid leakage.

Yet another particular object is to provide a tube assembly that maintains its working fluid tightness and insulation features with time.

These objects, as well as others which will be more apparent hereinafter, are achieved, according to claim 1, by a tube assembly for delivering working fluids in cleaning devices, comprising at least one pair of tubular members each having an outer protective tubular conduit adapted to house at least one inner tubular conduit for feeding of the working fluid. The inner and outlets conduits are telescopically mutually coupled along their respective longitudinal axes to adjust the length of the assembly. The inner conduits are made of a first plastic material which is easily continuously resistant to a relative high temperature of the working fluid, and the outer conduits are made of a second plastic material, different from the first material, which is not continuously resistant to the relatively high temperature.

Thanks to this particular arrangement, various kinds of high temperature working fluids may be used, which facilitate dirt removal and improve hygiene.

Preferably, the outer conduits have such diameters and thicknesses as to maintain, on their outer surface, a temperature below 30°C, when the working fluid has a temperature close to 100°C.

Thanks to this particular feature, the tube assembly may be used in an easy and safe manner, while preventing surface portions from being overheated and becoming dangerous.

Suitably, the inner conduits have such diameters and thicknesses as to be slide one into the other in a substantially tight manner. Furthermore, the tube assembly has sealing means proximate to the connection area between the inner conduits, which can stably resist to high temperature.

Thanks to this particular arrangement, a high working fluid tightness may be ensured, whereby any dangerous fluid leakages during use may be avoided.

Brief Description of the Drawings Further features and advantages of the invention will be more apparent from the detailed description of several preferred but non-exclusive embodiments of a tube assembly according to the invention, which are described as non-limiting examples with the help of the annexed drawings, in which: FIG. 1 is a partial view of a tube assembly according to the invention, in the retracted condition; FIG. 2 is a partial view of the tube assembly as shown in Fig. 1, in the extended condition; FIG. 3 is a partial view of a detail of the tube assembly of Fig. 1; FIG. 4 is a partial view of a further detail of the tube assembly of Fig. 1; FIG. 5 is a partial view of a third detail of the tube assembly of Fig. 1.

Detailed description of a preferred embodiment With particular reference to the above mentioned figures, a tube assembly according to the invention is described, which is overall designated with numeral 1, for feeding working fluids in cleaning apparatus.

The tube assembly 1 comprises at least one pair of tubular members 2,2', each having an outer protective tubular conduit 3,3'and at least one inner tubular conduit 4,4'. Each inner conduit 4, 4'is housed inside an outer conduit 3,3'and allows feeding of the working fluid.

Inner conduits 4,4'and outer conduits 3,3'are mutually telescopically coupled interconnected along their respective longitudinal axes Li, LE to adjust the length of the assembly 1.

Inner conduits 4,4'are made of a first plastic material which is easily continuously resistant to a relative high temperature of the working fluid, whereas the outer conduits 3,3'are made of a second plastic material, different from the first one, which is not continuously resistant to the relatively high temperature.

Thus, the plastic material to be used for outer conduits 3,3'may be less valuable and less expensive than the material to be used for inner conduits 4,4', thereby limiting overall manufacturing costs.

Suitably, the relative high temperature is of at least 100°C. This characteristic allows to use, as a working fluid, steam or heated cleaning fluids, which ensure a higher dirt removal and hygiene improvement capacity, as compared with ambient temperature working fluids.

The inner conduit 4,4'of each tubular member 2,2'is not monolithic, i. e. independent of its corresponding outer conduit 3,3', but is rigidly connected thereto. In other words, the inner conduit 4, 4'and the outer conduit 3,3'of each tubular member 2,2'are manufactured separately, using different materials, and are subsequently assembled, in such a manner as to be rigidly connected to each other, though still separable.

Such feature allows to detach the inner conduits 4,4'and replace them with other conduits or with conduits made of different materials, for better adaptation to

different working fluids.

Each inner conduit 4,4'is connected to its respective outer conduit 3.3'by at least one transverse end wall 5,5'.

Advantageously, each transverse end wall 5,5'is integral with its respective inner conduit 4,4'and has heat insulating connection means 6,6'for anchorage to its respective outer conduit 3, 3'. These transverse end walls 5,5'have the dual function of closing a longitudinal end of each outer conduit 3,3'and of connecting it to its respective inner conduit 4,4', by a properly heat insulating connection.

The heat insulating connection means 6,6'comprise a substantially cylindrical portion 7, 7', which extends from each transverse end wall 5, 5'parallel to its respective inner conduit 3,3'. Each substantially cylindrical portion 7, 7'has holes 8,8'for snap engagement with corresponding projections 9,9'of its respective outer conduit 3, 3'.

The inner conduit 4,4'of each tubular member 2,2'has a longitudinal axis LI which is substantially parallel to its corresponding outer conduit 3,3'.

Advantageously, each inner conduit 4,4'is connected to its respective outer conduit 3, 3'coaxially thereto. When a single inner conduit 4,4'is provided for each outer conduit 3,3', this coaxial arrangement allows to obtain an angularly uniform temperature profile over each cross section of the outer conduits 3,3'.

The outer conduits 3,3'have such diameters DE, DE'and thicknesses SE, SE'as to maintain, on their outer surface, a temperature below 30°C, when the working fluid has a temperature proximate to 100°C.

The inner conduits 4,4'have such diameters Di, Dl and thicknesses SI, SI. as to be able to slide one into the other in a substantially tight manner. Also, seal means 10 are provided at the connection between inner conduits 4,4'.

The seal means 10 may include one or more elastic rings 11, placed in appropriate annular seats 12 of at least one of the inner conduits 4,4'.

Suitably, the seal means 10 may further include a lip seal 13, positioned at one longitudinal end of an inner conduit 4,4. Such lip seal 13 is so designed as to expand and provide a sealing action, caused by the pressure inside the inner conduits 4,4'.

The base material of the seal means 10 is selected from the group of synthetic materials that stably resist to a temperature of at least 100°C, to prevent any dangerous leakage of the working fluid at a relatively high temperature, even after prolonged use.

The seal means 10 and the transverse end walls 5, 5'are so designed that the overall length of the tube assembly 1 may be varied from a minimum value which is slightly above the length of a tubular member 2,2'to a maximum value which is slightly below the sum of the lengths of the tubular members 2,2'.

The tubular members 2, 2'include locking means 14 adapted to selectively lock mutual sliding thereof.

Advantageously, the locking means 14 are so designed as to allow the tubular members 2,2'to be locked in predetermined mutual positions. In more detail, the locking means 14 may include a linear slider 15, which is fitted onto an outer conduit 3, and a stop member 16, which is operable by said linear slider 15 and engageable in a plurality of substantially equally spaced recesses 17, evenly arranged on the other outer conduit 3'.

From the foregoing it clearly appears that the tube assembly 1 according to the invention fulfils the intended objects and particularly the selection of materials for the inner conduits 4,4'and the seal means 10 allows to use high temperature working fluids, which facilitate dirt removal and improve hygiene.

Also, the non monolithic design of the inner conduits 4,4', relative to the outer conduits 3, 3'allows to limit manufacturing costs.

The tube assembly according to the invention is susceptible of a numerous modifications and changes all falling within the inventive concept disclosed in the appended claims. All the details thereof may be replaced by other technical equivalents, and the materials may vary according to the contingencies, without departing from the scope of the invention.

While the tube assembly has been described with particular reference to the accompanying figures, the numerals referred to in the disclosure and claims are only used for the sake of a better intelligibility of the invention and shall not be intended to limit the claimed scope in any manner.

This application is based on and claims priority of Italian patent application Vl2002A000206, which was filed in Italy on September 27th 2002, whose contents are expressly incorporated herein by reference.