The explosive bolt described above is appropriate for being used for such connections, which have to be openable rapidly due to an emergency situation. A large field of such use is for instance for mounting of vehicle doors and the new device is particularly useful for this purpose. Nowadays door hinge systems both for passenger cars and for lorries are constructed so, without exception, that it at a somewhat more violent collision is an evident risk, that vehicle doors get stuck, as a heavy demolition of the car body will compress doors as well as door openings. The axes of the hinges might also loose their parallelism and door locks can be damaged, and all this taken together can make opening of the car doors more difficult or even impossible after a violent collision, which in turn can cause dangerous situations of different degrees for passengers. Outer circumstances can also worsen accidental situations. Such an example is when a car turns over and possible obstacles at the ground such as rocks, ditches, different types of large objects, etcetera, can prevent the car doors from being opened. Furthermore it is also usual that passengers loose consciousness and it is then even more difficult for the rescue team to help them to come out of the vehicle.

The explosive charge in an explosive attachment device must be strong enough for causing the desired effect to separate the connected components, but this also leads to undesired side effects. If the device is constructed so, that it will be blasted completely to pieces, it is easy that there as a result is dangerous metal splinters, and also small volumes of appropriate explosive, which is commonly used in such circumstances, cause considerable force at the detonation, which can result in that the metal splinters will have a high velocity, which therefore have a large possibilty of penetrating through the typical thin sheet metal structures, which are common in car bodies and therefore the passengers are subjected to danger. The chock effect of the detonation is also undesired and means a risk e. g. for impared hearing to the

passengers. Furthermore the handling of the explosive components must be considered in connection to storing and transport and also at the time of production of the cars, and in case of a possible unintended detonation, the risk for personal injuries must be minimized.

There are a number of known proposals for explosive attachment devices in form of different versions of explosive bolts, which principally could be used for assembly of car door hinges in order to reduce the problems described above in connection to accidents. Such proposals are disclosed for instance in: US 5, 997, 230, US 3, 754, 496, US 2, 653, 504, US 3, 582, 017, US 1, 400, 401 and DE 2203470. These proposals are anyhow intended to be used primarily within space travel technology and for military use and for both these fields of use there are basically other conditions than for cars and for that reason the known solutions are not suited for mounting of car doors. In space travel persons are not directly subjected to detonations of explosive bolts with metal splinters, which is the case in cars. Within the military field, explosive bolts are e. g. used in mines and missiles and the like and the situation is quite the opposite, as any splinter may even be desirable.

It can furthermore be established that in the proposals mentioned above, the detonation takes place substantially immediately after initiation, without any time delay at all, and this is an impossible situation in respect of mounting of car doors with aid of explosive bolts. At a violent collision the cars are often making a passage through the air with tumbling motion and it is evident, that a loosening of the doors at a too early stage, could be nearly a catastrophy. The car must come to a stop and its position must be stabilized before it is time for the doors to be separated by detonation of any type of door hinge attachment.

PURPOSE AND MOST ESSENTIAL FEATURES OF THE INVENTION The purpose of the invention is to eliminate the shortages described above by providing a new type of explosive attachment device to be used for mounting of different mechanical components, e. g. vehicle doors, thus that the component when needed can be separated by means of a detonation without causing the passengers any risk, and of the type which is built in such a manner, that an explosive arrachment element pulls apart an attachment screw mounted therein by means of detonation without causing metal splinters or a violent shock effect and which attachement element is provided with a built in delayed-action firing device, which is

therefore protected and. in working order independent of external conditions. This has been achieved in that the explosive bolt according to the invention has been given the features defined in claim 1.

Hereinafter the invention will be further described with reference to an embodiment illustrated in the accompanying drawings.

In Fig. 1 is shown a cross-section of the proposed explosive attachment device.

In Fig. 2 iis Ilustrated in an exploded view in perspective an embodiment of a portion of the attachment device according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS In Fig. 1 is shown a cross section of an attachment device for interconnecting separate mechanical components (1), and which device incorporates an attachment screw (2) equipped with a washer (3) and an explosive attachment element (4-14). The screw (2) extends through the bores in the interconnected components (1) and is screwed into the attachment element (1-14) and therefore the components (1) are clamped together in usual manner between the attachment element (1-14) on one side and the washer (3), which is positioned under the head of the screw (2) on the other side.

The attachment screw (2) forming part of the device is provided with a head, the height of which along the circumference of the screw is dimensioned in such a manner, that an imagined cylindrical, vertical surface, which is an imagined extension of the envelope surface of the screw (2) inside the head of the screw (2) is substantially as big as the smallest transversal surface of the screw (2) and therefore this imagined surface forms the most weak section in the screw (2). The washer (3) in this connection has a particular task beside the ordinary of preventing the screw (2) from passing through the bores, i. e. to act as a shearing tool and for that reason it is necessary that the washer (3) is manufactured from a harder material than the screw (2) and also that it is shaped in an appropriate manner, thus that the bore of the washer (3) is sufficently much bigger than the diameter of the screw (2) with an appropriate tolerance, and furthermore that the edge of the hole is sharp.

The explosive attachment element (1-14) consists of a cylinder (4), which is equipped with a cover (5), which engages one of the interconnected components (1) adjacent the attachment bore, a piston (6) mounted inside the cylinder (4) and provided with a rod (7) extending in parallel to the longitudinal mean axis of the cylinder (4) and in

which rod (7) in the longitudinal direction of the cylinder (4) there is provided a threaded hole for the attachment screw (2), a locking washer (8) and an explosive charge (9) mounted in the cylinder (4) and having a firing device (10, 11, 12, 13).

In the center of the cover (5) is provided a hole parallel with the longitudinal mean axis of the cylinder (4) and intended for the rod (7), which extends closely through the hole, but anyhow so, that the rod (7) does not project outside the cover (5). In the edge in the side facing the cylinder (4) the cover (5) is provided with a collar, which for mounting of the cylinder (4) is equipped with an internal thread but not the entire way, but thus that there is a substantial distance between the thread and the bottom of the cover (5). The cylinder (4) is open in the end facing the cover (5) and it is closed at the opposite end and externally at the mouth there is a thread matching the thread at the inner side of the collar of the cover (5). The inner diameter of the cylinder (4) is substantially smaller than the inner diameter in the collar of the cover (5) and when the cover is mounted on the cylinder (4), the cylinder edge therefore will form a treshold in the inner wall of the closed space. The rod (7) is provided with a collar, the diameter of which is substantially larger than the diameter of the hole in the cover (5) in order to prevent the rod (7) from passing through the cover (5) and for transferring the mounting force via the cover (5) to the interconnected components (1). The piston (6) is mounted on the rod (7) by means of a threaded hole in the piston (6) and a corresponding thread on the rod (7). The piston (6) is provided with a shoulder thus that the outer diameter of the piston (6) at the side facing the cover is substantially smaller than the inner diameter of the cylinder (4), thus that the space between the cover (5) and the piston (6) increases. There is a thin and strong locking washer (8) with a central hole clamped between the piston (6) and the collar of the rod (7) in mounted position and which locking washer (8) has an external diameter, substantially as big as the inner diameter in the non-threaded part of the collar of the cover (5), but substantially smaller than the inner diameter of the cylinder (4). When the cover (5) is mounted on the cylinder, the locking washer (8) enters into the cover (5) thus that there is formed a space between the washer (8) and the bottom of the cover (5), and the piston (6) enters into the cylinder (4), thus that the edge of the cylinder (4) is pressed against the locking washer (8), which in turn acts upon the collar of the rod (7), thus that the rod (7) is held against the cover (5) and the position of the piston (6) is thereby locked inside the cylinder (4) when the cover (5) is mounted on the cylinder (4). Rotation at mounting of the attachment screw (2) can be prevented for instance by means of a stop screw, which is mounted through the wall of the cylinder (4), thus that it is pressed against the piston (6) and

in which piston (6) there is a corresponding groove thus that the stop screw will not prevent the longitudinal mean motion of the piston.

The cylinder (4) is substantially longer than the piston (6), which is arranged inside the cylinder (4) and positioned thus, that there is formed two chambers at opposite sides of the piston (6). In one of the chambers, which is limited of the cylinder (4), the piston (6) and the locking washer (8) there is mounted a sufficiently powerful explosive charge (9) and in the other chamber, which is limited by the piston (6) and the cylinder (4), there is provided a firing device (10, 11, 12,13) for detonation of the explosive charge (9). The firing device (10,11, 12,13) consists of a blasting fuse (10) packed in spiral form and which is provided with two igniting fuses (11,12), one fitted at each end and an electric cable which enters from outside via a hole in the bottom of the cylinder (4) and which cable (13) is connected to the adjacent igniting fuse (11).

The end of the blasting fuse (10), which is not connected to the electric cable (13) extends through a small hole through the piston (6), thus that the other igniting fuse (12) will be in contact with the explosive charge (9) in the chamber at the opposite side of the piston (6). In the wall of the cylinder (4) between the piston (6) and the bottom of the cylinder, there is, at a distance from the bottom of the cylinder (4) at least as big as the smallest height of the piston (6), a number of holes (14) of appropriate size arranged in a circular row, and which holes (14) are intended for pressure relief after a detonation.

When an external signal system couples electric current to the electric cable (13), the blasting fuse (10) is fired by means of one of the initiating fuses (11), which is connected to the electric cable (13) and in order to provide a long enough time delay for the detonation, the blasting fuse (10) thereafter burns for a sufficiently long time before the fire reaches the other initiating fuse (12) at the opposite end of the blasting fuse (10) at the other side of the piston. When this happens the initiating fuse (12) thereby initiates the explosive charge (9). The pressure which is generated as a consequence of the detonation then gives rise to power effects, which acts upon the piston (6), the cylinder (4) and the locking washer (8). The wall of the cylinder (4) is dimensioned thus that it is strong enough not to burst immediately, whereas the fixedly mounted locking washer (8), which is much weaker than the cylinder (4) and the piston (6), is broken and the piston (6) is thereby unbolted, and can now move and therefore transfer the shock effect via the rod (7) to the attachment screw (2) and effect a pulling stress in the attachment screw (2) and further a shearing load on the head of the screw (2). As the interconnected components (1) are positioned

between the washer (3) and the attachment element (1-14), the head of the screw (2) therefore is punched away by means of the washer (3). The pressure of the detonation urges the piston (6) to pull the rod (7) and the attachment screw (2) into the cylinder (4) and the mechanical coupling between the interconnected components (1) therefore is terminated. When the piston (6) passes the pressure relief holes (14) further away at the wall of the cylinder (4), the blasting gases are removed via the holes (14) and the pressure in the cylinder (4) is lowered without causing the device to burst apart. The dimensions of the cylinder (4), the rod (7) and the piston (6) are dimensioned thus that the rod (7) will stay inside the hole in the cover (5) when the piston (6) is in the bottom position and thereby the rod (7) prevents the blasting gases from being removed via the large hole in the cover (5) and cause undesired shock effects for the environment.

In Fig. 2 is illustrated a somewhat modified embodiment of the attachment device according to the invention in an exploded view, whereby the modification consists in that the rod (7) has been equipped with a non-round profile at the side facing the locking washer (8). In a corresponding manner the locking washer is equipped with a non-round recess matching the non-round profile of the rod. The locking washer (8) is furthermore provided with recesses (15) arranged at the circumference, and which correspond to projections (16) in the upper edge of the cylinder (4). In this manner the piston and the rod are prevented from rotating relative to each other during mounting of the attachment device. The non-round profile of rod and locking washer have been shown hexagonal, but it is of course possible to think of other non-round shapes. The circumferential recesses (15) in the locking washer (8) can also be exchanged for circumferential projections, whereas the cylinder (4) in that case has corresponding recesses.

The invention is not limited to the embodiment shown in the drawings and describend in connection thereto but modifications and variants are possible within the scope of the following claims.