In several areas of application there is a need for a rapid cutting or closing of the passage of, for example, power, water, gas and oil through cables, pipes and the like, or the severing of tension cables for security installations or other devices. These may, for example, include devices in land-based industry or offshore activities or devices for boats and ships, cars, leisure-time apparatus and so on.

The present invention relates in general to a device for the automatic cutting or closing of cables, wires, pipes and the like, wherein the cutting of the negative and/or positive cable of a vehicle is described below as a suitable area of utilisation.

When a vehicle is involved in an accident, such as an inter-vehicular collision or other impact, there is always a great danger of secondary damage, such as fire or inadvertent release of air bags and seat belt tensioning devices. These are elements of danger which may further injure the victim of the accident and which also constitute a danger for the rescue teams and ambulance personnel or other persons who attempt to come to the aid of the victims.

Fire breaks out, for example, when combustible materials, fuels or chemicals in or close to a vehicle are subjected to heat. Heat may be generated immediately due to an electrical short circuit (sparks/flashes) and sparks, or from heated elements such as the engine, exhaust system (catalytic converters) etc.

The systems for the release of air bags and seat belt tensioning devices are made so that they can in fact self-release after the power has been turned off (some US car models can store power for up to 30 minutes). An inadvertent release of these may be so powerful as to cause grave injury, even taking lives in some cases.

It is therefore of great importance that the negative and/or positive cable is cut as soon as possible after a crash, and therefore this is a task of high priority for the rescue teams that arrive at the scene of an accident. Today, this cutting of the cable is done with the aid of, for example, a cable cutter. It is a procedure which will inevitably take some time. The area around the battery may be damaged in the crash, and it may be difficult to gain access in order to cut the power cable. Thus, valuable minutes may be lost during the rescue work. When the cable is cut automatically in connection with the

collision, time is gained, possibly resulting in improved chances of survival for those involved in the accident.

In the case of this area of application, the task of the present invention is to provide a device for mounting on the negative and/or positive cable in all types of vehicles which in the event of a collision will automatically cut the cable. A device of this kind should be simple to install in cars, and should be relatively inexpensive to produce.

EP 0 638 458 Al describes a system for disconnecting the battery or batteries in an electrically powered vehicle in the event of an accident such as a collision. When a collision is detected, a signal is given to one or more devices which are placed in the immediate vicinity of the battery or batteries so that the connection is broken. The signal or signals ensure that an explosive charge in each device is fired and breaks the cable connection. However, there is no detailed description in this document of how the device which breaks the connection is constructed.

US 3,895,552 describes a device for severing cables, pipes, bolts and the like, wherein detonation gases from an explosive charge drive a piston including a knife blade towards the element to be severed. However, this document discloses nothing with regard to the use of the pressure from the detonation gases to move the severed pieces apart from another, nor anything as regards the structural features for adapting the device for use in exacting environments. However, as will become evident below, the last-mentioned properties are central features of the present invention.

Accordingly, based on the above example, a device is provided for cutting the negative and/or positive cable from the battery in a vehicle, wherein the driving power for the cutting operation is constituted by an explosive material which is actuated in the event of an impact, characterised in that it comprises a sensor means for transmitting an electrical impulse to an explosive material (a primer) arranged in a combustion chamber, a piston mounted in an insulating part with a cylinder arranged beneath the combustion chamber, which at the end facing away from the combustion chamber bears a cutting edge, wherein the unit comprising the combustion chamber and insulating part including a piston mounted in the cylinder encircles the cable and includes a holder means therefor. As previously mentioned, similar devices can, be used in different areas where there is a need for a rapid permanent break in the supply of power, liquid or gas, or to break a cable, wire or the like.

It is of major importance that the device of the invention in its different fields of application withstands the surrounding environment. Water, steam, gases, dust particles and the like may cause functional faults if they affect the primer, corrode the cutting edge, lock the piston in the cylinder housing or the like. An essential structural feature of the invention is therefore to mount the parts which appear vulnerable to external environmental impact so that they are encapsulated in a sealed manner. This also increases considerably the applicability of the device according to the invention, since it can be placed in different environments, even"tough"ones.

In connection with the above-mentioned use of the device according to the invention as part of a security system, it is an essential feature of the invention that the device can be retrofitted without disconnecting the cable, pipe or the like at either of their ends. This structural feature is provided in one embodiment in that the part of the device which encircles the cable or pipe is split, and that once the cable or pipe has been put in place the parts are held together in engagement around the cable or pipe with the aid of a fastening means (not shown). This may, for example, be a screw/thread connection between the parts, an encircling (metal) band with a clamp or the like. To enable the device to function correctly, it is however crucial that the fastening means chosen is capable of taking up the forces which arise after actuation of the explosive material.

The invention thus provides a device as disclosed in the preamble of the attached independent claim 1, and which is characterised by the features disclosed in the characterising clause.

Advantageous embodiments are disclosed in the attached dependent claims.

The invention will be described in more detail below with reference to the attached drawings, wherein: Figure 1 is a cross-sectional view of a first embodiment of a device according to the invention mounted on the negative cable.

Figure 2 shows the device in Figure 1 after detonation of the primer and cutting of the cable.

Figure 3 is a cross-sectional view of a second embodiment of a device according to the invention mounted on the negative cable.

Figure 4 shows the device in Figure 3 after detonation of the primer and cutting of the cable.

Figure 5 is a cross-sectional view of a third embodiment of a device according to the invention mounted on the negative cable.

Figure 6 shows the device in Figure 5 after detonation of the primer and cutting of the cable.

Figures 1 and 2 show a primer (1) which in the event of an impact receives an electrical impulse from a sensor (not shown). This impulse ignites the powder charge (2). A substance known in the art such as"sodium acid"may, for example, be used as the powder charge. Alternatively, the primer may receive its impulse from a sensor arranged in the same system as the sensor system for air bags or belt tensioning devices.

The powder charge (2) will be ignited instantly and will generate combustion gas. This creates a high pressure in the combustion chamber (I)and causes the piston (3) with cutting or closing edge (13) to be pressed down through the power cable (7).

When the piston knife is in its lower position, the overpressure which has been generated inside the combustion chamber l) and the cylinder in parK, II ? will be passed down into an overpressure channel (4) and will in fact act to expel the severed cable (7) and the cable ejector (6). This is done to ensure that renewed contact between the cable parts does not occur. In the method used today, the cut ends of the cable must be insulated, and in practice this is done by winding insulating tape around them. In the devices according to the invention, the severed parts, once cut, will be automatically encapsulated in insulating material, and no further handling will be required.

Reference numeral (5) indicates a spring which is pretensioned and which expels the cable ejector (6) which in turn clamps the cable (7) and draws the cable with it as it is expelled. As mentioned,"press force"from the overpressure also plays a part. The cable ejector (6) clamps the cable (7) and ensures that it is ejected once it has been cut.

The cable ejector remains in position as long as the cable is fastened to the cable holder (9). On the inside of the cable ejector there may in fact be a thin O-ring or the like which prevents water and moisture from entering the system.

The reference numeral (8) indicates a stopper of, for example, rubber, which prevents water and moisture from entering the system and which is forced out when the piston is in its lower position.

The illustrated cable holder (9) clamps around the cable and is screwed into the insulating part II. On the inside of the cable holder there may again in fact be an O-ring

or the like which keeps water and moisture away from the system. In the whole device sealing against penetration of moisture is ensured by means of gaskets or O-rings, stoppers and the like. These may be made of a conventional material, for example, a suitable silicone material.

As described above, it may be desirable to release one end of the cable, pipe or the like, so that after actuation of the primer this end is prevented from coming into contact again with the other end. Figures 3 and 4 show a second embodiment of the invention which differs from the previously described embodiment, shown in Figures 1 and 2, primarily in that the pretensioned spring (5) is not included, but that the pressure from the detonation gases against the internal, exposed surfaces of the cable ejector (6) alone causes this, and the cable or pipe (7) around which the cable ejector clamps, to be ejected from the insulating part II.

Figures 5 and 6 show a third embodiment of a device according to the invention, wherein the cable ejector (6) is not included, but wherein the ejection function is provided in that the diameter of the groove holding around the cable in the insulating part II is different on each side of the cutting groove. Where the diameter is smallest, the device clamps around the cable or pipe (7), whilst the diameter on the other side is greater than the diameter of the cable or pipe. Thus, one of the cut ends will be free after release, whilst the device forms a fixed, insulating termination of the other end.

When the piston (3) and cutting or closing edge (13) is in its lower position, the overpressure generated inside the combustion chamber I and the cylinder in part II, can, as in the first embodiment, be passed down in front of the cut cable (7) and eject it.

Parts which are identical and/or have the same function in all three embodiments have the same reference numerals in the attached drawings.

In these second and third embodiments of the invention the sealed encapsulation of the environment-vulnerable parts is secured by making the insulating part II and cylinder with a closed floor or membrane below the cutting or closing edge (13). The piston (3) and cutting or closing edge (13) can be mounted inside the cylinder before the cylinder head I with primer (1) is mounted in the top of the device. When the primer (1) is set off, the piston will press the cutting or closing edge (13) through the membrane (12) before it strikes the element that is to be cut or closed.

The cutting or closing member under the piston (3) may be in the form of a plate (11) having a width greater than the diameter of the piston, and wherein corresponding

recesses in the cylinder wall form guiding grooves for the plate during its movement in the cutting or closing operation.

The device according to the invention may preferably be made of materials which render it as light as possible. As an example, part I may be made of a light metal, such as aluminium. The holder part of the device, indicated by II, may be made of an insulating material, such as, for example, a plastic material. Another possibility would also be to make the whole device of hard plastic.

The device according to the invention will be easily mountable at a suitable point on existing cables, pipes or the like. The design of the device is relatively simple and it can therefore be produced without being excessively costly. In addition, the device is highly flexible as regards choice of impulses which are to set off the primer, wherein the actuation can take place manually, automatically, by preprogramming or the like.