The invention relates to a flexible plastics tubing provided for transmitting a signal, wherein the tubing at a first end includes a signal input member, and at a second end includes a signal readout member.

It is commonly known that flexible plastics tubing, in particular hoses for vacuum cleaners, in use, bridge a distance between the driving unit and the user. A disadvantage associated therewith is that the user, to turn the unit on or off or to change a particular setting, needs to walk over to the driving unit and hence, needs to go back and forth over this distance. This poses a problem, both with conventional vacuum cleaners as with integrated central vacuum systems. This is the main reason why, for example, vacuum cleaners keep running even if the user is not vacuum cleaning but, for example, moving a chair. For a short to medium break in vacuum cleaning, many users will not bother to turn off the vacuum cleaner. This causes a large loss of energy. Moreover, the lifetime of the vacuum cleaner will decrease more than necessary, because the vacuum cleaner is turned on for a longer time than necessary. A solution has been devised to solve this problem, namely by providing a signal input member at one end, and a signal readout member at another end of the tubing.

Such a hose is known from WO2006/095151 (Smiths group PLC, 2006), considered to be the closest prior art, and from US 4693324 (Automation Industries, Inc., 1987). In said hose, at least two copper wires are integrated extending from one end to another end of the hose and connected there to the signal input member and the signal readout member. A signal can be transmitted from one end of the hose to the other end of the hose over these two copper wires, such as an on/off signal, such that the user does not have to walk over to the driving unit. This allows for a smooth on/off switching of the vacuum cleaner.

A disadvantage of said known hose is that copper is expensive. Furthermore, incorporating a copper wire into a plastics hose is difficult and complex, such that the maximum production rate will be low. Furthermore, the flexible hose with copper wire will be heavy and not very flexible due to the high specific weight and the bending properties of copper, and due to the extra plastics to be added in order to obtain enough rigidity and insulation around the copper wire. Because the hose is heavy and not very flexible, it is difficult to handle such during vacuum cleaning. Furthermore, in order to reuse said hose, the copper needs to be separated from the plastics, which is a complex process. Therefore, in case of production failures, wherein commonly the plastics of the flexible hose may directly be reused, firstly the copper should be separated from the plastics.

Such a hose is also known from US 2008/0066252 (Herron, Roy Howard JR, 2008), offering a further solution to the problems arising from the processing of a copper wire in a plastics hose, as explained above. This hose is provided at one end with a radio frequency transmitter and is provided at another end with a radio frequency receiver. In this way, communication over the hose is made possible without substantial modifications to the hose itself. A disadvantage of this method is that it is expensive. Also, batteries should be provided with the radio frequency transmitter, which is a disadvantage because it is not environmentally friendly, as the latter need to be replaced from time to time, and the transmitter will simply not work when no correct batteries are available.

It is an object of the invention to provide a flexible plastics tubing for transmitting a signal and which can be manufactured cheaper, lighter and more flexible than the tubing from the prior art.

To this end, the flexible tubing according to the invention is characterized in that said tubing comprises at least one zone extending continuously from said first end towards said second end to be connected to the signal input member and the signal readout member respectively, wherein said at least one zone is made of a conductive plastics. Conductive plastics, contrary to copper, has very similar properties to conventionally used plastics for flexible tubing. This will make the processing of conductive plastics in a flexible plastics tubing easy. Furthermore, the specific weight and the bending properties of conductive plastics are similar to that of conventionally used plastics for flexible tubing, such that conductive plastics in such a tubing will have no negative effect on the weight and bending properties of the tubing.

Preferably, said at least one zone comprises two zones at a distance from each other extending continuously from said first end towards said second end and wherein the tubing at least between said two zones is made of a non-conductive plastics. This allows a closed electrical circuit to be formed between the signal input member and the signal readout member, over which a signal is capable of being transmitted. In one embodiment, said at least two zones extend continuously from said first end towards said second end and at least one, preferably two zones may be connected to the signal input member and/or the signal readout member, respectively.

Within the context of this application the wording "tubing for transmitting a signal" is to be interpreted as tubing, suitable to carry a transmitted signal, generate a signal or transmit a signal, for example a signal based on a property of the conductive plastics, such as electrical resistance. Preferably, said signal readout member comprises means to measure an electrical resistance between said two zones. Contrary to a copper wire, which has a conductivity that allows it to be integrated in a switching circuit of a drive, a conductive plastics has a very low conductivity. This very low conductivity does not allow to simply replace the copper wire with a conductive plastics. Preferably, an adapted signal readout member is provided to perform a resistance measurement. This allows for the measurement of a change in resistance between the conductive zones, resulting from a switch at the signal input member and hence, a signal is capable of being transmitted.

Preferably, said signal input member comprises a mechanically operated switch and said signal readout member an electrically operated switch provided to switch, based on a comparison between a measured electrical resistance and a predetermined set resistance. In this way, turning a switch at the signal input member may switch a circuit at the signal readout member. Due to the relatively low conductivity of conductive plastics compared to copper, a resistance measurement will be preferred over direct switching of the circuit at the signal readout member using the input member.

The invention will now be described using an embodiment shown in the drawing.

In the drawings :

Figure 1 shows a schematic arrangement of an embodiment of the invention ;

Figure 2 shows a transversal sectional view of a tubing with conductive zones ;

Figure 3 shows a longitudinal sectional view of a tubing with conductive zones, and Figure 4 shows an electrical diagram of a signal readout member.

In the drawing the same or analogous element is assigned the same reference numeral.

Figure 1 shows a schematic arrangement of the invention and shows at the left side a signal input member 2, in the middle the flexible plastics tubing 1 with at least one conductive zone 3 and at the right side a signal readout member 4.

The signal input member 2 is depicted as a push button, which is able to generate an on/off signal by switching between a maximum resistance (open state of the switch) and a minimum resistance (closed state of the switch). Other types of signal input members 2 other than push buttons may also be applied in the invention. For example, the signal input member 2 may be formed by a knob, for example formed by a potentiometer, which step-by-step or continuously changes a resistor to generate a signal. Likewise, the signal input member 2 may be an electronic circuit which generates a digital signal comprising a series of ones and zeros.

The flexible plastics tubing 1 according to the invention comprises at least one zone 3 which continuously extends from one end of the tubing to the other end of the tubing, and which is made of a conductive plastics. Through one zone, a signal may be transmitted by applying an electrostatic interference at one side of the tubing 1 , which interference is detectable on the other side. However, preferably, two zones 3 are provided in the tubing, as shown in the figures, which are each manufactured of a conductive plastics. Between these two zones 3 a non- conductive plastics is located, such that these two zones 3 are not interconnected in the tubing 1. These two zones 3 are at the ends of the tubing connected to the signal input member 2 and the signal readout mem- ber 4, respectively. Hence, an electrical circuit is formed and an electrical signal can be transmitted from one end of the tubing 1 at the signal input member 2, to the other end of the tubing, at the signal readout member 4.

Preferably, the zones 3 with the conductive plastics in the tubing 1 are fully embedded in a non-conductive plastics. Hence, the zones are completely surrounded by non-conductive plastics. Hence, for example a drop of water 5 attached to the inside or outside of the tubing 1 is not able to achieve an electrical contact between the two zones 3. Consequently, the failure rate of such a system with a flexible tubing with a two conductive zones 3 is substantially improved.

Typically, flexible plastics tubing are corrugated tubing. Such corrugated tubing may typically be manufactured using two processes. According to a first process, an intermediate tubing is extruded as an intermediate step in the process, which intermediate tubing is subsequently forced by blow molding or vacuum molding into a corrugated tubing. According to a second process, a corrugated profile is extruded which is subsequently wound such that a tubing with said corrugated profile is obtained. Both processes allow to apply the invention, as will be explained further below.

To apply the invention in a tubing which is manufactured according to said first process, an intermediate tubing may be extruded with a cross section as shown in Figure 2. This intermediate tubing consists of two zones 3 which extend longitudinally between the beginning of the intermediate tubing towards the end of the intermediate tubing. By blow or vacuum molding said intermediate tubing, a flexible corrugated tubing 3 is obtained wherein the two zones 3, following the corrugations, run longitudinally from the beginning of the tubing 1 to the end of the tubing 1. This will cause the distance a signal must bridge across the three zones to be minimal. Because conductive plastics exhibit a significant electrical resistance, as explained further below, it will be desirable that said distance will be as small as possible. The advantage of the flexible tubing with conductive zones, produced by said first process, will therefore be that the length of the zones 3 is minimal.

To apply the invention in a tubing 1 which is manufactured according to said second process, an profile may be extruded with cross section as shown in Figure 3. This cross section will form the longitudinal section in the flexible tubing 1. This profile is coiled in a spiral shape, in which adjacent parts of the profile are interlinked, such that one flexible corrugated tubing 1 is obtained. Herein, the zones will spirally extend from the beginning of the tubing to the end of the tubing. The distance an electrical signal must bridge will therefore be larger than the length of the tubing. However, since the extruded profile is wound, and therefore not substantially distorted, also the diameter of the zone 3 will not be deformed. This allows the resistance of the zone 3 over the wound distance to be properly controlled, which is less evident in a tubing produced according to the first process. With the tubing produced by the first process, the cross section of the zone 3 is negatively influenced by the blow or vacuum molding.

A further advantage of manufacturing the flexible tubing according to said second process is that the size of the cross section of the zone 3, and its location in the corrugated profile, can be determined freely. Hence, a thickening in the radial wall portion, being that part of the wall that is essentially perpendicular to the axis direction of the tubing, will have no substantial effect on the flexibility of the tubing. In Figure 3, the zones 3 are positioned in the radial wall portions, making this wall portions thicker than the wall portions in the rest of the profile. By increasing the size of the cross section of the zone 3, as is obtained by thickening the wall portions as shown in Figure 3, a better signal transmission is obtained as the electrical resistance decreases.

The signal readout member 4 preferably comprises means for measuring the electrical resistance. These means are connected with the two zones 3 to measure the electrical resistance between these zones 3. Furthermore, the signal readout member 4 comprises an electrical switch which is provided to switch based on a comparison between a measured electrical resistance and a predetermined set resistance. In this way, the signal readout member 4 may switch an electrical circuit based on the position of the signal input member 2.

An example of the signal readout member 4 is shown in Figure 4. The diagram shows on the left two connecting elements 6 to which respectively the first and second conductive zone 3 of the tubing 1 can be connected. The diagram shows, for illustration, a number of resistors R1 , R2, R3, R4 and R5, a number of transistors, TR1 , TR2, TR3, a 9V power supply, a capacitor C1 , a potentiometer VR1 and two LEDs L1 and L2. The whole is constructed such that, when there is an infinite resistance between the two connecting elements 6, the LED L2 is active and the LED L1 is not active, and when there is a resistance of about 5.10 ⁷ ohm (5.10 ⁷ equals 5 times 10 to the seventh power) between the two connecting elements 6, the LED L1 is active and the LED L2 is inactive. Hence, an electrical circuit is obtained, based on resistance. Furthermore, the whole is entirely constructed such that the sensitivity of the system is ad- justable by the potentiometer VR1 .

Within the scope of the invention, reference is made to electrostatic conductive plastics when the resistance over the plastics is between 10 ohm and 10 ⁵ ohm. Reference is made to electrostatic dissipative conduc- tive plastics when the resistance over the plastics is between 10 ⁵ ohm and 10 ¹¹ ohm. Reference is made to insulating plastics when the resistance over the plastics is larger than 10 ¹¹ ohm. A test setup is built and successfully tested, wherein the measured resistance was approximately 5.10 ⁷ ohm.

According to the invention, it will also be possible to transmit a signal from the signal readout member, the vacuum cleaner, to the signal input member, the handle, over the flexible tubing 1. For instance, on the handle of the vacuum cleaner, the content of the dust bag could be visu- alized.