|Title of Invention
AN ELECTROMECHANICAL SAFE-ARM DEVICE FOR CONTROLLING PYROTECHNICALLY ACTUATABLE SYSTEMS
|This invention relates to an electromechanical safe-arm device useful ro provide safety to the pyrotechnically actuatable systems in rokets and missiles. It consists of a limited rotation bi-directional torque motor, the stator of which is housed in the safe-arm body and the rotaing part, which carries the magnet and a pair of detonators. Rotation of the motor shaft aligns and dealigns the detonators with respect to the receptor ordnance in the 'arm' and 'safe' positions respectively. The unit also features shorting/grounding of detonators in 'safe' provision for connecting the detonator leads to the power source in arm, as well as electrical indication of status by means of a two position rotary switch. "Bidirectional Torque" is what a motor can provide and not by which a motor is not disclosing about the invention.
This invention relates to an electromechanical safe-arm device for direct and remote control of pyrotechnically actuatable systems. The safe-arm control device is particularly useful in rockets, missiles and the like to ensure safety of the vehicle, personnel and installation by preventing inadvertent initiation of major ordnance systems in them. The device is also flexible, as it can be mounted directly on any system or may be used for remotely controlling the same.
Ordnance systems in rocketry perform critical functions such as solid motor ignition, staging, heat-shield jettisoning and flight termination (destruct). All these systems are initiated using electro-explosive devices (EED). Safe/arm system protects the ordnance system from inadvertent initiation of EEDs caused by stray electric impulses such as static electricity, radio frequency (RF) & electro magnetic interference (EMI) and also due to wrong electric commands.
The subject invention is a safe-arm device which consists of a pair of electric initiators (detonators) and their receptor ordnance, which can be either 'Through Bulkhead initiators' (TBI) or Explosive transfer assembly (ETA) lines. The detonators are housed in the core of a limited rotation DC torque motor. The receptor elements are housed in the body of the device, which also carries the stator part of the motor. The motor is actuated to cause (a) movement of the detonators 90°C out-of-line (safe position) and in-line (arm position) w.r.to the receptor ordnance and (b) shorting and grounding of the detonator electrical leads (safe poisition) and removing the
short and connecting the leads to the power source (arm position). In the safe position, any accidental triggering of initiators gets terminated within the device, thus preventing further propagation. A rotary switch, whose movement is also concurrent to movement of actuation motor, gives indication of safe and arm position to remotely mounted panels. The unit can be electrically moved between arm/safe positions. Manual safing provision also exists. A spring loaded ball-detent mechnism ensures 'hand-safety' of the device, ie. it prevents movement to arm position due to mechanical disturbances.
The device contains dual initiators and receptor elements, thereby providing redundancy for explosive elements.
Conventional electromagnetic safe-arm devices used in launch vehicles are either of the two types viz. 'direct mounting' t\pe which is generally used for solid motor ignition applications, is mounted on the head end of the solid rocket motor igniter and tbrms part of a solid rocket motor (SRM) or the 'remote mounting' type which is mounted at a convenient location away from the SRM and provides the input stimulus to the ordnance system by means of explosive transfer lines. In addition to ignition, the remote mounted units are used for applications such as staging, heat shield jettisoning and vehicle destruct systems. The above types of safe/arms use either rotary solenoids or DC motors with internal planetory gears to provide motive force. Most of these devices carry an intermediate explosive charge in addition to the EEDs (Electro-Explosive Devices) and receptor elements.
A direct mounting device has the advantages that it is less complex compared to the remote mounted type, but its mounting constraints adds to system height and further, since it forms part of the SRM, the necessity to withstand high chamber pressures makes it heavy compared to the other type. Further, due to the high chamber pressures, features such as visual indication of safe/arm status and provision for manual safing of the device are usually absent in direct mounting devices. A remote mounting safe arm, on the other hand, has the obvious merit that it can be positioned at convenient locations to help monitoring of visual status, external to the structure. Further, in contrast to the direct mounting type, mating of its electrical connectors for the initiators can be timed late in the count-down sequence thereby enhancing safety of the system. Also, such an arrangement can be used to assist weight balancing of the rocket or spacecraft. However, the system is more complex as it includes a number of components such as gears, clutch mechanisms etc., is comparatively e^qjensive and contains more number of electrical lines and ordnance-train elements.
The subject invention aims at development of a simple device with lesser complexity, lesser system cost and flexibility to be used both as direct and remote mounted device with the merits of both versions mentioned above. In addition, all the important features existing in safe-arm devices used presently in operational launchers are incorporated.
To develop a safe-arm device which can satisfy the following:
1. to inhibit accidental initiation of ordnance systems by mechanical interruption of the explosive train along with electrical shorting of initiators and to enable initiation train when called upon.
2. to provide for safe-to-arm and arm-to-safe operations through remote electric command using a limited rotation torque motor.
3. to permit use as a direct mounted device also as a remote mounted device with minor external hardware changes.
4. to permit use of a through bulk heat initiator (TBI) in the direct mode and thereby provide a non-frangible bulk head to preclude hot gas leakage during and subsequent to SRM ignition.
5. to permit manual safing but prohibit manual arming.
6. to provide remote electrical and visual indication of safe and arm positions.
7. to provide mechanical safety through providing pins or keys which prevents rotation of the barrier in safe position.
8. to provide redundancy in firing train.
9. to provide independent circuits for firing line and for control and monitoring.
This invention relates to an electromechanical safe-arm device for direct and remote control of pyrotechnically actuatable systems which comprises a body housing at least one detonator holder containing detonator, a limited rotation shaft carrying a 2 pole magnet, a stator assembly for
actuating rotation of the said shaft to dealign and align the detonators to safe and arm positions respectively and a two position rotary switch mounted on the said shaft to connect electrical leads of the said detonator to a power source in arm position and short in the safe position.
The rotary switch is preferably a pair of wafer switches. These switching wafers make and break electrical contact with the detonator leads on rotation of the shaft to a predetermined degree. The second wafer of the switch gives electrical signals for safe and arm position and also provides for electrically controlling movement between safe/arm positions. The body may be made of aluminium alloy. The two pole magnet is bonded to the detonator holder which houses two detonators.
Accordingly the present invention provides an electromechanical safe-arm device of direct and remote mounting modes for of pyrotechnically actuatable systems comprising a body housing atleast one detonator holder containing detonator, a limited rotation shaft connected to two pole magnet and stator assembly for actuating the rotation of said shaft and a two position rotary switch being mounted on said shaft, electric leads of said detonator being connected at one position to a power source and is shorted at the other position of said two position rotary switch, said stator on energization rotates the shaft to dealign and align said detonator with respect to receptor ordnance in safe and arm position respectively.
This invention will now be described with reference to the single figure shown in the accompanying drawings.
The configuration shown in the drawings permits the use of direct mounting and remote mounting with minor alterations to aid interfecing and assembly. In both the direct and remote modes, a barrier is provided by moving the primary explosive element namely, the detonator out of line with the receptor ordnance. Means are also provided for shorting and grounding of electrical initiators in "safe* position and connecting them to the firing leads in 'arm' position. The device is directly mounted to a system through a through bulkhead initiator which carries secondary high explosives and pyrotechnic charges required for ignition. The device also is provided with interfacing means for receiving explosive transfer assembly for transferring the stimulus to the ordnance system when the device is to be used in remote mode.
The motor is of dual winding and is of limited rotation type. It is electrically commanded for bidirectional rotation for a predetermined angle. The stator provides the necessary magnetic field for movement of the internal rotating member.
The device consists of a body (5) which houses the detonator (I) in detonator holder (7). The rotor shaft is indicated by numeral (6). The stator (4) is connected to a two pole magnet (8). The rotary switch is indicated by numeral (10). Numeral (2) stands for the through bulkhead initiator when the device is to be directly mounted. Reference is to be directly mounted. Reference numerals 9,11,13,14,16 and 17 are bearing holder, lock screw.
safmg pin, groove for inserting the safing pin, six pin receptacle and mounting holes respectively. Reference numeral (12) represents the cover for the body (5).
The rotor assembly is supported by bearings and the two pole magnet is bonded to the detonator in detonator holder which houses two detonators. In the safe position, these detonators which are 180° apart are positioned 90° offset with respect to the receptor elements. Inadvertent initiation of the detonators in this position does not get propogated to the bulk initiator, due to angular offset. Rotation of the detonator holder - rotor assembly by 90°C causes the detonator and the receptor element to get aligned so that initiation of the detonator transfers the stimulus to subsequent receptor element. This is called the arm position.
The rotor shaft carries a two position rotary switch (10). The electrical leads from the power supply for firing detonators terminate on the switch. The leads from the detonators are soldered to the switch contacts. As governed by the angular specification of the switch it maintains a short across the detonator leads and also keeps it grounded in the safe position. In 'arm' position the shorting and grounding are removed and the detonator leads gets connected to the leads from the power source. The switch also provides indications for safe and arm position and also for the electrical movement between safe/arm positions from the operating control console.
Though this invention has been described hereinabove with respect to a specific embodiment alterations and modifications known to persons skilled in the art are not excluded from the scope of the appended claims.
1. An electromechanical safe-arm device of direct and remote mounting modes for of pyrotechnically actuatable systems comprising a body housing atleast one detonator holder containing detonator, a limited rotation shaft connected to two pole magnet and stator assembly for actuating the rotation of said shaft and a two position rotary switch being mounted on said shaft, electric leads of said detonator being connected at one position to a power source and is shorted at the other position of said two position rotary switch, said stator on energization rotates the shaft to dealign and align said detonator with respect to receptor ordnance in safe and arm position respectively.
2. The device as claimed in claim 1 wherein the body is made of aluminium alloy and is provided with a cover.
3. The device as claimed in claims 1 and 2 wherein said two position rotary switch consists of a pair of wafer switches.
4. The device as claimed in claim 3, wherein signals are provided by one of the wafer switches to indicate safe and arm position.
5. The device as claimed in claims 1-4, wherein interfacing means are provided for receiving explosive transfer assembly.
6. The device as claimed in claim 1, wherein said rotor has two way windings and is electrically commanded for bidirectional rotation in a predetermined angle.
7. The device as claimed in any of the preceding claims wherein the two position rotary switch is provided with grounding /shorting means and means for powering the detonators in arm position.
8. An electromechanical safe-arm device substantially as herein described with particular reference to the accompanying drawings
Dated this 16 day of August 2000
|Indian Patent Application Number
|PG Journal Number
|Date of Filing
|Name of Patentee
|INDIAN SPACE RESEARCH ORGANISATION
|DEPARTMENT OF SPACE, ANTRARIKSHA BHAVAN, NEW BEL ROAD, BANGALORE 560 094,
|PCT International Classification Number
|PCT International Application Number
|PCT International Filing date