WO2010103495A1

WO2010103495A1 - Shape-memory supply cable

Info

Publication number: WO2010103495A1
Application number: PCT/IB2010/051080
Authority: WO
Inventors: Paolo Cappellari
Original assignee: GIURIANI STEFANO
Current assignee: GIURIANI STEFANO
Priority date: 2009-03-13
Filing date: 2010-03-12
Publication date: 2010-09-16
Anticipated expiration: 2011-09-13
Also published as: ITMI20090387A1

Abstract

A supply cable for a portable device comprising at least one pair of separate, electrically conductive wires kept together with dielectric material is disclosed, comprising a wire made of shape-memory material, having an overall low-bulk embryonic shape, as well as induction electric heating means apt to impart to said shape-memory wire a temperature at least equal to its critical temperature at which it returns to said embryonic shape, said heating means using a resistance conductive element wherein a current obtained from a network power socket of the supply cable is made to flow.

Description

SHAPE-MEMORY SUPPLY CABLE DESCRIPTION FIELD OF THE INVENTION

The present invention refers to a supply cable for small portable devices, such as household appliances, music readers, and so on. BACKGROUND

As known, electric and electronic portable devices (such as small household appliances, mobile telephones, PDAs, laptops and so on) are normally powered through flexible, often removable cables, provided with a plug for connection to the mains power socket. Sometimes they incorporate also an electric energy storage battery, which is periodically recharged through a supply cable which can be connected to the home electric system. Since portable devices typically do not comprise also a transformer, which would take up space and increase the weight thereof , the supply cable is usually provided also with a transformer body (arranged between a plug and the supply cable) , suited to transform network current (in Italy alternated current at 220 V and 50 Hz) into recharge current (for example direct current at 5 V) .

The supply cable or supply device (consisting of a supply cable and of the transformer) is sufficiently long (often in the order of 1-2-m) and is used to meet the temporary need, but is then stored elsewhere when it does not perform its function. Of course, when storing it away, it is desirable for it to take up as little space as possible, especially if the user is a frequent traveller and hence he needs to find space in his/her travel bags . The transformer body and the electric connection plug have an own bulk, dictated by technical functionality as well as by electric and thermal requirements which cannot be reduced at will. Conversely, the electric supply cable - at the end of which a small plug for connection to the device to be recharged is arranged - can be compacted efficiently.

While during usage it is useful and convenient for the ca- ble to remain stretched - because it allows to arrange the appliance into a position convenient for the user, regardless of the position of the wall electric socket - when not in use the cable can be wound to dramatically reduce its bulk and obstruc- tion.

This requirement is not limited to the electric supply cables of a battery charger, but extends also to other contexts wherein a thin leading wire is provided which, during use, must remain substantially stretched and can instead be compacted when not in use. Such a condition occurs, for example, also in the case of supply cables of earphones or headphones .

The users of these portable devices know very well that a simple way to accomplish bulk reduction provides to wind the cable on itself, or to wind it on an auxiliary body (the trans- former body or the same portable device) , before storing it away into a drawer or a bag.

According to the prior art, other systems for achieving the same result in a more rational way have also been suggested.

For example, it has been provided to couple the supply ca- ble with an elastic thread-like element, which tends to maintain a compact shape, for example a spiral arrangement. A typical application of this technical solution is with the electric supply cables of a number of electric shavers. When not in use, the electric cable tends to maintain a wound arrangement, with a certain number of same-diameter coils, aligned along an axis and close to one another, when the user, during use, wishes to stretch the cable to extend the range thereof, it is sufficient that he imparts a traction to elastically open the coils and increase the distance between the supplied device and the plug in- serted in the wall socket.

However, this solution is not always effective and appealing because, in whatever use condition, it implies the constant presence of an elastic return force, against which the user must impart a retaining action to keep the cable stretched. Another prior-art solution provides instead the use of actual winding mechanisms, possibly provided with elastic return means. In such case, when not use, the supply cable is wound on a suitable mechanism, from which it is unwound for a desired length whenever necessary. The rewinding in the mechanism can occur manually or by elastic return means, which can be loaded during unwinding and triggered voluntarily by the user. This mechanism has a much more appealing and effective operation, compared to the above indicated approach. However, it is rather complex, expensive and is prone to jamming and/or failure. A winder example is illustrated in US2005/042914. JP06-087573 discloses the use of shape-memory material to wind and temporarily transport very long material .

US 2004/0248434 discloses the use of shape-memory material as conductor within small electronic instruments with printed circuits, to ease assembling operations. The object of the present invention is hence to solve the above-mentioned problems, suggesting an innovative supply cable assembly for portable devices, which keeps the desired extension during use and can be compacted effectively with the minimum bulk when not in use. Such object is achieved through a supply cable as described in its essential features in the attached claims.

In ' particular, according to a first aspect of the invention, a supply cable for a portable electric device comprising at least one pair of separate, electrically leading wires kept together with dielectric material is provided, wherein a shape- memory cable is integrated, having a low-overall-bulk embryonic shape, as well as heating means apt to impart to said shape- memory cable a temperature at least equal to its critical temperature of return to said embryonic shape. According to a preferred aspect of the invention, the heating means of the supply cable comprise an electric charge capacitor connected so as to discharge its charge into a heat- induction current .

According to a further aspect of the invention, the heating means of the supply cable comprise instead a manually operable switch, apt to convey network current into a heating resistance of the cable .

Further features and advantages of the device according to the invention will in any case be more evident from the following detailed description of some preferred embodiments of the same, given by way of a non-limiting example. DETAILED DESCRIPTON OF PREFERRED EMBODIMENTS

A supply cable provides, in a way known per se, at least one pair of electrically conductive cables apt to transfer electric charges with a voltage difference ranging from a few mmV - as in the case of its use with earphones and other low-voltage devices - to several dozens V - as in the case of apparatuses supplied directly with a network voltage, for example of 110-220 V - by a power source to an appliance.

The two leading wires, typically made of copper alloy, are kept electrically separate and are kept together into a single cable by means of one or more sheaths or jackets of dielectric material, preferably plastic material, such as for example PVC.

At one end of the supply cable there is provided a standard or proprietary plug apt to connect to a socket of the specific device to be supplied, for example to the socket of the battery charger of a mobile phone, PDA, laptop, or to the socket of the audio output of an MP3 player, and so on. At the other end of the supply cable a user device or appliance is provided, such as a pair of earphones, or a supply socket, possibly provided also with a current transformer body.

According to the invention, said supply cable further has, coupled with or integrated in the two leading wires, a third wire of shape-memory metal material .

In this context, as shape-memory material the wide class of metal alloys (such as Ni-Ti, but also others) which have the peculiarity of recovering a preset macroscopic shape, due to the change of temperature (in particular the exceeding of a critical temperature) is mainly understood, that is they are capable of undergoing reversible crystallographic transformations, depend- ing at least on their thermal state. It is expected that also other, not strictly metal, materials may fall within this defi- nition, even if the metal composition has some advantages which will be evident in the following description.

Preferably, the wire of shape-memory metal material has a length substantially equal to that of the supply cable and is fastened/ coupled with, or integrated in said cable. For example, the shape-memory wire can be integrated into the same plastic sheath enclosing the two leading wires, during an additional assembling phase on top of the one in which the two leading wires insulated with dielectric material are manufactured. Alterna- tively, the shape-memory wire can be embedded into the dielectric matrix during the same extrusion phase in which the electrically conductive wires are also mutually coupled and insulated in the supply cable.

According to the invention, the shape-memory wire, before being coupled with the conductive supply cables, undergoes a suitable thermal treatment - known per se in the sector of shape-memory materials - so as to impart it an overall low-bulk shape, which the cable will tend to take up whenever it is heated above a critical temperature (determined by the specific material and by its size) : in the following, such low-bulk shape will be referred to as the "embryonic shape" of the specific shape-memory wire. The embryonic shape imparted to the wire can be for example helical with identical coils aligned on an axis, or spiral with concentric coils developing on a same plane or others. It can also be provided that, in its embryonic shape, the cable arranges itself along a flat design, for example in the distinctive shape of the manufacturer of the device to be supplied, which would impart the supply cable further added value . The phase of coupling the shape-memory wire with the conductive wires can occur both in the embryonic shape state and - better - after having stretched in a substantially rectilinear way the shape-memory cable .

Embedded in or coupled with the supply cable, there are further provided means for heating by electric induction the shape-memory wire. Such heating means are provided to heat by electric induction the shape-memory wire at least up to the critical temperature, which causes the wire to return to its embryonic shape .

According to a preferred embodiment, such heating means are shaped as an electric capacitor - arranged for example in the body of the plug connecting to the wall socket, or in the transformer body - electrically connected to the supply cable so as to induce, when desired, a current which causes the heating of the shape-memory wire. The heating current can be caused to flow directly in the shape-memory wire, if it is a metal one, or in a parallel wire with electric resistance, suitably provided for such purpose .

The capacitor is mounted in the electric circuit to which the two leading wire belong, so as to charge during use of the supply cable. The accumulated charge is hence available - also upon removal of the supply cable from the network power socket - to cause a heating current for the shape-memory wire. The sizing of the capacitor must be proportional to the sizing of the shape-memory wire and to the speed at which the same is intended to be heated. Preferably, the capacitor is mounted in the electric circuit of the supply cable so that, upon removal of the plug from the wall current socket, the circuit closes automatically and the discharge of the capacitor is triggered, thus causing the automatic heating of the shape-memory wire and re- turn to the embryonic shape.

According to an alternative embodiment, it is provided that the electric circuit of the supply cable comprises a switch (for example a button micro-switch) , which can be actuated by the user, which closes a circuit which causes a flow of current (coming directly from the mains socket) in an electric wire with a resistance or in the same shape-memory wire, to an extent sufficient to cause a heating at least up to the critical temperature. In this case, operation is guaranteed only if the supply cable is connected to a power source, such as the home power network or an auxiliary battery. The heating means, in this case, comprise the switch and the network current induction cir- cuit .

The switch can also be of the automatic-return, button type, apt to simply temporarily mutually short-circuit the two conductive power supply wires of cable, causing a temporary heating of the cable. In such case it is preferable that in the supply cable - better, in the transformer body, if provided - a current limiter be arranged. In such case the user would keep the button depressed until the cable has taken up its embryonic shape . The switch apt to switch the electric circuit and induce heating current may also be provided on the appliance (for example on the mobile phone), instead of on the supply cable. In such case the switch is suited to convey current (coming from the supply cable or from the device battery) towards a suitable pole of the connecting plug of the supply cable, which then transfers it to the resistance element heating the shape-memory wire.

During use, the user stretches the supply cable at will as long as necessary; the supply cable, due to the properties of the shape-memory wire, tends to maintain this attitude without requiring the action of any retaining force. When use is over, by simple removal from the wall socket or by acting on the switch, the user can cause the wire to heat up and hence a fast return thereof to its embryonic low-bulk shape. Through the configuration described here, the objects set forth in the premises are brilliantly achieved. As a matter of fact, the supply cable according to the invention can be stretched without special effort, deforming also the shape- memory wire. The stretched shape is maintained by the shape- memory wire as long as it is useful for the purposes of the operation, for example until the charge of the mobile phone or of an electric shaver has run out. When use is over, it is sufficient to trigger the heating means to heat the shape-memory wire beyond its critical temperature and thereby cause it to return to its embryonic shape which has been suitably conceived to cause minimal bulk and/ or obstruction of the cable. Since no elastic return mechanism is provided, all opportunities for jamming and/or failure are fully removed.

Advantageously, the embryonic shape of the shape-memory wire can be designed with appealing aesthetic criteria and/or product-characterising criteria, which imparts further added value to the supply cable according to the invention.

Furthermore, the supply cable thus conceived has the automatic feature of signalling the appliance overload. As a matter of fact, should the appliance start to function irregularly, ab- sorbing excess current, heating of the supply cable would occur, resulting in the supply cable suddenly taking up its embryonic shape, which would be immediately evident to the user as a sign of malfunctioning.

However, it is understood that the invention is not limited to the particular embodiments illustrated above, which represent only non-limiting examples of the scope of the invention, but a number of changes are possible, all within the reach of a person skilled in the field, without departing from the scope of the invention . For example, it is not ruled out that the shape-memory wire can be obtained with a suitable conductive metal alloy, so that it can be one of the leading wires : in such case the supply cable would have only two wires .

Furthermore, it is not ruled out that the shape-memory wire can be made of a material which is neither metal nor an electric conductor and can hence be heated by means of a further resistance wire, coupled therewith, within which current for induction heating is caused to circulate.

Moreover, although the inventive principles have always been expressed with reference to a supply cable for small portable devices, it is not ruled out that the invention may be applied also in other contexts, by means of suitable adaptations, for example in the building of an extension supply cable for domestic or gardening use wherever it is necessary to repeatedly wind and unwind a supply cable between different moments of the use thereof. Finally, although reference has always been made to a continuous coupling between the shape-memory wire and the supply cable, it can also be provided that the coupling be discontinuous along the linear extension of the cable, for example by means of annular bands or welding points outside a conventional electric cable.

Claims

1. Supply cable for a portable device comprising at least one pair of separate, electrically conductive wires kept together with dielectric material, characterised in that it com- prises a wire made of shape-memory material, having an overall low-bulk embryonic shape, as well as induction electric heating means apt to impart to said shape-memory wire a temperature at least equal to its critical temperature at which it returns to said embryonic shape, said heating means using a resistance con- ductive element wherein a current obtained from a network power socket of the supply cable is made to flow.

2. Supply cable as claimed in claim 1) , wherein said heating means comprise an electric charge capacitor connected so as to discharge its charge into a current in said resistance con- ductive element inducing heat in said shape-memory wire.

3. Supply cable as claimed in claim 2) , wherein said electric charge capacitor is apt to discharge upon the removal of said supply cable from a network power supply socket .

4. Supply cable as claimed in claim 1), wherein said heat- ing means comprise a manually operated switch apt to convey network current into said resistance element apt to heat said shape-memory wire .

5. Supply cable as claimed in claim 2 ) or 4 ) , wherein said resistance conductive element is the very shape-memory wire.

6. Supply cable as claimed in claim 4) , wherein said switch is apt to short-circuit said pair of electrically conductive wires .

7. Supply cable as claimed in claim 4) , 5) or 6), wherein said switch is provided on an appliance with which the supply cable can be coupled.

8. Supply cable as claimed in any one of preceding claims , wherein said shape-memory wire makes up one of the wires of said pair of electrically conductive wires .

9. Supply cable as claimed in any one of the preceding claims, wherein said shape-memory wire is embedded in said dielectric material .

10. Supply cable as claimed in any one of claims 1) to 7) , wherein said shape-memory wire is distinct from said pair of electrically conductive wires .