Ordnance – Explosive operated apparatus
Reexamination Certificate
2002-03-11
2004-01-13
Carone, Michael J. (Department: 3641)
Ordnance
Explosive operated apparatus
C102S202100
Reexamination Certificate
active
06675692
ABSTRACT:
The present invention relates to a pyrotechnic actuator according to the preamble of claim
1
.
A generic actuator is known from U.S. Pat. No. 4,091,621. The U.S. Pat. No. 4,091,621 shows a pyrotechnic actuator, in the case of which an explosive is electrically ignitable, whereby the gas arising moves a piston. A lock prevents the piston returning from its terminal position to its initial position. In this case the locking action is provided by a c-shaped clamp ring held in a circumferential groove of the piston, which in the compressed, that is to say spring-loaded condition lies in the cylinder with the piston. As soon as the piston is moved out of the cylinder by the developing gas, the tensioned, c-shaped ring can de-tension, as a result of which its radius becomes greater than the inner radius of the cylinder. Also in the de-tensioned condition the c-shaped ring remains in the groove of the piston. If the piston tries to move back again to its initial position, the c-shaped ring strikes the head of the cylinder and prevents the piston from entering the cylinder.
A disadvantage with this embodiment according to U.S. Pat. No. 4,091,621 is that the piston is only retained in its position by friction. This friction stops when the c-shaped ring has left the cylinder. Secure anchoring of the piston in its initial position is however not assured by friction. If it is further considered that such systems must be ready to operate but are not used over a long period, the locking requirement cannot be met by means of friction. This is especially therefore the case, since there is no guarantee that the tension in the c-shaped ring is maintained for several years by the metal. If for example the pyrotechnic actuator is used in a vehicle, this must still be completely functional after 10 or 20 years. This is only guaranteed if the piston always remains in its initial position.
The aim of the present invention is therefore to provide a pyrotechnic actuator, in which the piston is securely retained in its initial position. This aim is achieved according to the invention by a pyrotechnic actuator with the features of claim
1
. Further advantageous embodiments of the object of the invention are clear from the features of the sub-claims.
Through the use of a snap-in element and/or a sprung retaining element the piston is advantageously retained in the initial position. Corresponding elements can for example be sprung contact studs or snap connections. The action of the elements guarantees in this case that simply by applying minimum force to the piston it can be moved from its initial position to the terminal position. Through the use of corresponding ratchet- or retaining elements the necessary minimum force can be pre-determined precisely. This is an important advantage compared to the known friction, which is affected by several factors and which can only be inadequately calculated. In addition the necessary minimum force for moving the piston from the initial to the terminal position does not change over time, since for example a sprung contact stud as an initial position retaining element is not stressed by force, but force is only applied on it when the piston is moved. As a result metal fatigue is prevented advantageously.
The ratchet- or retaining elements used advantageously at the same time to serve as retaining elements, which retain the piston in the terminal position after this has been reached. This means that advantageously no extra parts are required and therefore the retaining function in the initial as well as in the terminal position can be realised with few parts.
Advantageously several ratchet- or retaining elements can be provided so that the piston is prevented from going back to the initial position, not just after reaching the terminal position, but also on the way from the initial position to the terminal position it is prevented by the several ratchet or retaining elements, after passing one of the elements, from going back from this position to the initial position.
Advantageously both the ratchet as well as the retaining elements can together ensure the piston is locked. In this case all locking mechanisms, which in particular are the embodiments illustrated in the figures, can be used in combination with one another.
Advantageously the ratchet- and/or retaining elements are moulded or secured on the piston or the cylinder itself. In this case for example as snap-in or retaining elements a contact stud or bow-spring can be used, which for example interacts with a saw-tooth shaped surface structure or engages in appropriately functional cavities, so that the piston can move in relation to the cylinder each time in only one direction after overcoming a minimum force.
An especially preferred embodiment of a pyrotechnic actuator is the case if the piston has a cavity extending in the lengthwise direction of the piston, into which a stud on the housing engages as the gripping mechanism, whereby the ratchet or securing elements work together with the pin or stud fixed rigidly on the housing. The pin or stud together with the longitudinal cavity or oblong window-type aperture acts as a bearing and guide for the stud. In this case the ratchet or retaining elements are arranged on the piston itself.
If the piston is an injection moulded part, the ratchet- or retaining elements can be formed by means of a plate inserted in the piston, whereby for example the plate advantageously forms the wall of the oblong cavity or window-type aperture, so that the stud can securely slide in the oblong cavity or window-type aperture. Through the use of a suitably curved and stamped metal plate to form the inner wall as well as the ratchet or securing elements, the piston can also be reinforced, as a result of which greater forces can be applied by the piston itself to trigger a particular operation.
Through the advantageous use of an oblong cavity or window-type aperture for the interplay with a locking pin or stud, the ratchet or securing elements can be designed so that the pin or stud pivots or moves the ratchet or securing elements to the side when the piston moves from the initial position to the terminal position, whereby after passing the ratchet or securing elements these are moved back to their initial position either by an external spring or bending force stored in the element itself. The ratchet or securing element with positive locking then prevents the locking stud from moving against the movement direction from the initial position to the terminal position in the piston past the ratchet- or securing element to its initial position.
Positive locking is achieved particularly advantageously if the ratchet- or securing element is a contact stud, which fully passes through the window-type aperture, so that if the stud is moved with its free end in relation to the piston against the movement direction from the initial to terminal position, it is pressed by the stud against a stop. Only by destroying the ratchet or locking element can the piston now be moved back to its initial position. Through corresponding design of the ratchet or locking element however the force necessary for destruction can be calculated in such a way that destruction by forces acting on the piston from outside is not possible.
Advantageously the electrical detonator together with any necessary explosive is arranged directly in the cavity of the housing and therefore in the cylinder of the pneumatically operated cylinder. The electrical detonator has electrical ignition contacts, which are fed out from the cavity through at least one aperture, so that they can be connected to an ignition circuit. The housing of the pyrotechnic actuator is designed to advantage in such a way that in the unassembled condition of the pyrotechnic actuator the electrical connections of the detonator are short-circuited by means of a short-circuit element. This short-circuit element can be secured on the housing by means of a snap-connection; it is however also conceivable that the short-circuit element is injection moulded dir
Carone Michael J.
Factor & Partners
Sukman Gabriel
LandOfFree
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