Abstract
A method for rotating a toggle link upon an acceleration event greater than a predetermined threshold. The method including: biasing a toggle link against a stop when the acceleration event is less than the predetermined threshold, a position of the toggle link against the stop being on a first side of a singular position of the toggle link; biasing the toggle link towards an opposite direction from the stop when the toggle link is positioned on a second side of the singular position; and moving the toggle link from the first side of the singular position to the second side of the singular position when the base structure undergoes an acceleration event greater than a predetermined threshold.
Claims
1. A method for rotating a toggle link upon an acceleration event greater than a predetermined threshold, the method comprising: biasing a toggle link against a stop fixed to a base structure such that there is no relative movement between the stop and the base structure when the acceleration event is less than the predetermined threshold, a position of the toggle link against the stop being on a first side of a singular position of the toggle link; biasing the toggle link towards an opposite direction from the stop when the toggle link is positioned on a second side of the singular position; moving the toggle link from the first side of the singular position to the second side of the singular position when the base structure undergoes an acceleration event greater than a predetermined threshold; and one of opening or closing an electrical circuit upon the toggle link being moved to the second side of the singular position; wherein the moving comprises providing a movable mass disposed between the toggle link and the base structure, the movement of the mass moving the toggle link to the second side of the singular position when the base structure undergoes an acceleration event greater than a predetermined threshold.
2. The method of claim 1, wherein the base structure and the toggle link positioned on the first side of the singular position are angled towards each other and the mass has a wedge shape having first and second sides complementary to angles of the base structure and the toggle link when positioned on the first side of the singular position.
3. A method for rotating a toggle link upon an acceleration event greater than a predetermined threshold, the method comprising: biasing a toggle link against a stop fixed to a base structure such that there is no relative movement between the stop and the base structure when the acceleration event is less than the predetermined threshold, a position of the toggle link against the stop being on a first side of a singular position of the toggle link; biasing the toggle link towards an opposite direction from the stop when the toggle link is positioned on a second side of the singular position; moving the toggle link from the first side of the singular position to the second side of the singular position when the base structure undergoes an acceleration event greater than a predetermined threshold; and initiating a pyrotechnic element upon the toggle link being moved to the second side of the singular position; wherein the moving comprises providing a movable mass disposed between the toggle link and the base structure, the movement of the mass moving the toggle link to the second side of the singular position when the base structure undergoes an acceleration event greater than a predetermined threshold.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) These and other features, aspects, and advantages of the apparatus of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:
(2) FIG. 1 illustrates a schematic of a cross-section of a thermal battery and inertial igniter assembly.
(3) FIG. 2 illustrates a schematic of a cross-section of an inertial igniter for thermal battery described in the prior art.
(4) FIG. 3 illustrates a schematic of the isometric drawing of the inertial igniter for thermal battery of FIG. 2.
(5) FIG. 4a illustrates a schematic of a cross-section of a thermal battery with an inertial igniter positioned on the top portion of the thermal battery and in which the ignition generated flame to be directed downwards into the thermal battery compartment.
(6) FIG. 4b illustrates a schematic of a cross-section of a thermal battery with an inertial igniter positioned on the bottom portion of the thermal battery and in which the ignition generated flame to be directed upwards into the thermal battery compartment.
(7) FIG. 5 illustrates a schematic of cross-section of an inertial igniter for thermal battery described in prior art with an outer housing.
(8) FIG. 6a illustrates a schematic of the first embodiment of an inertia igniter configured to initiate pyrotechnic materials when subjected all-fire spin rate.
(9) FIGS. 6b-6e illustrate the inertia igniter of FIG. 6a in various stages of spin rates.
(10) FIG. 7a illustrates a schematic of an electrical G-switch configured to close (open) when it is subjected to a prescribed spin rate.
(11) FIGS. 7b1, 7b2 and 7c illustrate the schematic of details of general configuration of the contact elements of a normally open version of the electrical G-switch of FIG. 7a.
(12) FIG. 7d illustrates the schematic of the electrical G-switch of FIG. 7a in its activated configuration.
(13) FIGS. 8a and 8b illustrate the schematic of details of general configuration of the contact elements of a normally closed version of the electrical G-switch of FIG. 7a.
(14) FIG. 8c illustrates the schematic of the electrical G-switch of FIG. 8a in its activated configuration.
(15) FIG. 9a illustrates a schematic of another embodiment of an inertia igniter configured to initiate pyrotechnic materials when subjected all-fire axial (setback) accelerations of relatively low amplitude and/or low duration.
(16) FIG. 9b illustrates the inertia igniter of FIG. 9a in its activated configuration following an all-fire setback acceleration.
(17) FIGS. 9c-9d illustrate view “A” of FIG. 9a, showing the operation of the striker link release mechanism of the inertia igniter of FIG. 9a.
(18) FIG. 10 illustrates a schematic of another embodiment of an inertia igniter configured to initiate pyrotechnic materials when subjected all-fire spin acceleration for use in so-called spinning rounds, i.e., rounds that are fired by rifled gun to gain high spin rate about their long axis for stability upon gun barrel exit.
(19) FIG. 11 illustrates an overall isometric view of an inertial igniter of one of the disclosed embodiments packaged in housing with flame exit opening.
(20) FIG. 12 illustrates the assembly of two or more (in this illustration three) packaged inertial igniters shown in FIG. 11 on a single platform for assembly inside a thermal battery for providing two or more independent means of thermal battery initiation to achieve very high level of thermal battery initiation reliability.
(21) FIG. 13 illustrates an overall isometric view of a G-switch of one of the disclosed embodiments packaged in housing.
(22) FIG. 14 illustrates the assembly of two or more (in this illustration three) packaged G-switches shown in FIG. 13 on a single platform for providing two or more independent means of detecting all-fire condition to achieve very high level of all-fire condition detection reliability.
(23) FIG. 15 illustrates an alternative means of releasing the rotary striker of the inertial igniter of the embodiment of FIG. 10 under all-fire spin acceleration via the controlled breakage of a shear pin.
(24) FIG. 16 illustrates another alternative means of releasing the rotary striker of the inertial igniter of the embodiment of FIG. 10 under all-fire spin acceleration via a detent pin.
DETAILED DESCRIPTION
(25) One embodiment 100 of the present inertial igniter invention is shown in the schematic of FIG. 6a. In this embodiment, the striker component of the inertial igniter 100 is a toggle type of mechanism with the toggle link 101, which is attached to the structure of the inertial igniter 102, by a pin joint indicated with numeral 103. In its rest and normal position shown in FIG. 6a, the striker (toggle) link 101 is biased to rest on its right-most position shown in FIG. 6a, against the stop 104, by the spring 105. The spring 105 is preloaded in tension, and serves as the toggle mechanism spring, and is attached to the structure 102 on the end 107 and to the striker link 101 on the other end 108, preferably with pin or pin-like joints. The elements 106 and 114, fixed to the striker link 101 and the inertial igniter structure 102, respectively, are the two components of the ignition pyrotechnic. Alternatively, a one piece pyrotechnic element may be used, in which case the element 106 is preferably the ignition impact mass or pin and the element 114 is preferably the one piece impact initiated pyrotechnic element.
(26) The inertial igniter 100 is intended to be used in spinning munitions and is designed to activate by centrifugal forces generated by the spinning of the round about its long axis as described below. In the schematic of FIG. 6a, the inertial igniter 100 is being viewed along the long axis of the spinning round with the axis of spinning rotation (center of rotation of the inertial igniter as viewed in the schematic of FIG. 6a) is considered to be at the point 109.
(27) The operation of the embodiment 100 is as follows. At rest, the striker link 101 is biased to the right of the line 115 that passes through the pin joint 103 of the striker link 101 and the attachment point 107 of the spring 105, and leaving the striker link 101 attachment point 108 of the spring 105 to the right of the said line 115. When the munitions using the inertial igniter 100 is fired and begin to spin, the centripetal acceleration acts on the inertia of the element 110, generating a centrifugal force that will tend to push the element 110 in the direction of the arrow 111, against the surface 112 of the inertial igniter structure 102 and the side 113 of the striker link 101. If the munitions spin rate is high enough, it would generate a large enough centrifugal force on the element 110 in the direction of the arrow 111 to overcome the force exerted by the spring 105 on the striker link 101 to press it against the stop 104 and preventing it from rotating in the counterclockwise direction. As the aforementioned spin rate keeps increasing, the centrifugal force acting on the element 110 increases, thereby beginning to rotate the striker link 101 in the counterclockwise direction as shown in the schematic of FIG. 6b, until the attachment point 108 of the spring 105 reaches the line 115 as shown in FIG. 6c, i.e., until the toggle mechanism (striker) link 101 reaches its so-called singular position. With any further increase in the spin rate, the striker link 101 is further rotated in the counterclockwise direction and passes the aforementioned singular position, and the tensile force of the spring 105 will accelerate it rotationally in the counterclockwise direction (at least partially aided by further motion of the element 110 in the direction of the arrow 111) as shown in FIG. 6d. The striker link 101 will keep rotating in the counterclockwise direction with accelerating rate until the pyrotechnic components 114 and 106 impact and cause ignition. The latter state of the striker link 101 is shown in dashed lines in FIG. 6e.
(28) The flames and sparks generated by the ignition of the pyrotechnic material 114 and 106 is then routed out from provided ports, usually through a hole such as the hole 120 to below the base to initiate the thermal material pyrotechnics. In some applications the flames and sparks are required to be routed from the side or from the top (opposite to the direction of exit from the hole 120) side of the inertial igniter 100.
(29) It is noted that if the center of mass of the striker link 101 is away from the pin joint 103, then as the device spins, the resulting centripetal acceleration would act on the inertia of the striker link 101, generating a centrifugal force that would tend to rotate/keep the striker link 101 towards/at the aforementioned singular position shown in FIG. 6c. For this reason, the striker link 101 can be constructed such that its center of mass is located at the pin joint 103 or as close to it as possible.
(30) In general, the tensile preloading of the spring 105 and the inertia (mass) of the element 110 are selected such that if the munitions in which the inertial igniter is installed is accidentally dropped (in the direction of accelerating the element 110 in the direction of the arrow 111) or if the said munitions is made to gain spin rates that falls below the all-fire spin, or in case of any specified accidental events, the resulting counterclockwise rotation of the striker link 101 would always be less than required to bring it to (even close) to its aforementioned singular position shown in the schematic of FIG. 6c. Then following any one of such accidental events, the preloaded spring 105 would force the striker link to return to its initial inactivated state shown in the schematic of FIG. 6a.
(31) The inertial igniter 100 can be readily modified to operate as a so-called electrical G-switch upon activation by the aforementioned all-fire spin rate would close (open) a normally open (closed) electrical circuit. One embodiment 150 such a G-switch is shown in the schematic of FIG. 7a. The construction and operation of the electrical G-switch is identical to those of the inertial igniter 100 of FIGS. 6a-6d, except that the pyrotechnic components 106 and 114 of the inertial igniter 100 is replaced by contact and circuit closing (opening) elements described below.
(32) The schematic of the electrical G-switch 150 is shown in FIG. 7a. In this embodiment, the pyrotechnic component 114 of the inertial igniter 100 (FIG. 6a) is replaced with the contact element 151 and its pyrotechnic component (or striker pin) element 106 by the contact bridging element 152. All other elements of the G-switch 150 are indicated with the same numerals as the inertial igniter 100 of FIG. 6a.
(33) The close-up view “A” of the contact element 151 is shown in the schematic of FIG. 7b1. The contact element 151 is fixed to the structure 102 of the device and is constructed with at least two contacts 153 and 154, which are mounted on an electrically non-conductive base 157. The contact element 151 is also provided with conductive wires 155 and 156, which are connected to the contacts 153 and 154, respectively. The electrically conductive wires are passed through the electrically non-conductive base 157 as shown in FIG. 7a to prevent them from making contact.
(34) It is appreciated by those skilled in the art that if the structure 102 of the G-switch 150 is constructed with electrically conductive material, then the conductive wires 153 and 154 have to be routed out of the electrically non-conductive base 157 (from the side as shown in FIG. 7a or through a hole in the electrically conductive base of the structure 102—not shown in FIG. 7a). In applications in which the G-switch is attached, for example, to a printed circuit board 161 as shown in FIG. 7c, the electrically non-conducting base 157 is preferably mounted over a provided opening 159 in the structure 102 as shown in FIG. 7c, preferably in a provided recess 160, thereby allowing the contact wires 162 and 163 to pass through the provided opening 159 to reach the underlying element (in this case the printed circuit board 161). The wires can then be connected to the appropriate circuit provided over or bellow the circuit board 161—not shown).
(35) The close-up view “B” of the contact element 152, FIG. 7a, is also shown schematically in FIG. 7b2. The contact element 152 consists of an electrically non-conductive base 165, which is fixed to the surface of the link 166 (101 in the inertial igniter 100 of FIG. 6a) as shown in FIG. 7a. An electrically conductive contact strip 164 (which can be relatively thin and flexible) is mounted on the surface of the electrically non-conductive base 165.
(36) The electrical G-switch 150 operates in a manner similar to the inertial igniter 100 of FIG. 6a-6e, i.e., as the aforementioned spin rate is increased and reaches certain predetermined threshold, the link 166 begins to rotate in the counterclockwise direction. As the spin rate is further increased, the link 166 rotates further in the counterclockwise direction, until at a predetermined spin rate, the link 166 reaches its aforementioned singular position (as shown for the striker link 100 in the schematic of FIG. 6c). With further increase in the spin rate, the striker link 166 is further rotated in the counterclockwise direction and passes its aforementioned singular position, and the tensile force of the spring 105 will accelerate it rotationally in the counterclockwise direction (at least partially aided by further motion of the element 110 in the direction of the arrow 111) as shown in FIG. 6d for the inertial igniter 100. The link 166 will then keep rotating in the counterclockwise direction with accelerating rate until the contact strip 164 of the contact element 152 comes into contact with the contacts 153 and 154 of the contact element 151 as shown in the schematic of FIG. 7d. As a result, the wires 155 and 156 are connected electrically, and the circuit to which they are connected is closed.
(37) It is appreciated by those skilled in the art that more than two contacts 153 and 154 may be provided on the contact element 151, thereby allowing the electrically conductive strip 164 of the contact element 152 to close more than one electrical circuit (when using pairs of contacts 153 and 154 and electrically isolated electrically conductive strips 164 on the contact elements 151 and 152, respectively) or allowing at least three contacts (similar to contacts 153 and 154) on the contact element 151 to form a junction by an electrically conductive strip 164.
(38) The electrical G-switch 150 of FIG. 7a is designed for closing an electrical circuit once the G-switch is activated. Alternatively, the electrical G-switch 150 can be designed for opening an already closed electrical circuit by replacing the pair of contact elements 151 and 152 shown in FIGS. 7b1 and 7b2. In such an alternative embodiment of the present invention, the alternative pair of contact elements may be constructed in many different configurations. As an example, the contact elements 151 and 152 may be replaced by alternative contact elements 171 and 172, respectively, which are shown in the close-up views “C” and “D” in the schematics of FIGS. 8a and 8b.
(39) As can be seen in the close-up view “C” of FIG. 8a, the contact element 171 is fixed to the structure 102 of the electrical G-switch, and is constructed with at least two electrical contacts 173 and 174, which are mounted on an electrically non-conductive base 175. The electrical contacts 173 and 174 are fabricated of electrically conductive material commonly used in electrical contacts, are configured such that they are normally in contact as shown in FIG. 8a, and can be relatively flexible so that they could be pushed apart the required amount without causing them to permanently deform, i.e., such that they would return to their contacting configuration after separation of a relatively small amount as described below for their proper operation as a normally closed G-switch. The contact element 171 is also provided with conductive wires 176 and 177, which are connected to the contacts 173 and 174, respectively. The electrically conductive wires are passed through the electrically non-conductive base 175 as shown in FIG. 8a to prevent them from making contact.
(40) It is appreciated by those skilled in the art that as described for the normally open G-switch embodiment 150 of FIGS. 7a, if the structure 102 of the G-switch is constructed with electrically conductive material, then the conductive wires 176 and 177 have to be routed out of the electrically non-conductive base 175 (from the side as shown in FIG. 8a or through a hole in the electrically conductive base of the structure 102—not shown in FIG. 8a). In applications in which the G-switch is attached, for example, to a printed circuit board 161 as shown in FIG. 7c for the contact element, the electrically non-conducting base 175 (157 in FIG. 7c) can be mounted over a provided opening (similar to the opening 159 in FIG. 7c) in the structure 102 as shown in FIG. 7c, such as in a provided recess 160, thereby allowing the contact wires 176 and 177 (wires 162 and 163 in FIG. 7c) to pass through the provided opening 159 to reach the underlying element (in this case the printed circuit board 161). The wires can then be connected to the appropriate circuit provided over or bellow the circuit board 161—not shown).
(41) The close-up view “D” of the contact element 172 is shown schematically in FIG. 8b. The contact element 172 consists of an electrically non-conductive base 178, which is fixed to the surface of the link 166 (FIG. 7a) as shown in FIG. 8b. An electrically no-conductive (preferably relatively thin but rigid) plate 179 is mounted on the surface of the electrically non-conductive base 178. The tip 180 of the electrically non-conductive plate can be relatively sharp to facilitate insertion between the contacts 173 and 174 during the G-switch activation as described below.
(42) The electrical G-switch 150 with the normally closed contacts 171 and 172 operates in a manner similar to the aforementioned normally open G-switch shown in FIGS. 7a and 7d, i.e., as the aforementioned spin rate is increased and reaches certain predetermined threshold, the link 166 begins to rotate in the counterclockwise direction. As the spin rate is further increased, the link 166 rotates further in the counterclockwise direction, until at a predetermined spin rate, the link 166 reaches its aforementioned singular position (as shown for the striker link 100 in the schematic of FIG. 6c). With further increase in the spin rate, the striker link 166 is further rotated in the counterclockwise direction and passes its aforementioned singular position, and the tensile force of the spring 105 will accelerate it rotationally in the counterclockwise direction (at least partially aided by further motion of the element 110 in the direction of the arrow 111) as shown in FIG. 6d for the inertial igniter 100. The link 166 will then keep rotating in the counterclockwise direction with accelerating rate until the tip 180 of the electrically non-conductive plate 179 is wedged in the space 181 between the contacts 173 and 174; spreads the contacting surfaces of the contacts 173 and 174 apart; and is inserted between the contacts 173 and 174 as shown in the schematic of FIG. 8c. As a result, the contact between the contacts 173 and 174 is interrupted, and the circuit connected to the wires 176 and 177 is opened.
(43) It is appreciated by those skilled in the art that the spin rate that is required to achieve activation of the inertial igniter 100 of FIG. 6a-6e and electrical G-switches 150 of FIGS. 7a-7d and 8a-8c can be varied by varying the inertia and geometry of the element 110, the angles between the surface 112 of the structure 102 of the device and the surface 113 of the link 101 as seen in the schematic of FIG. 6a. In addition, the surfaces 112 and 113 as well as the contacting surfaces of the element 110 may be formed as curved to achieve the desired levels of counterclockwise rotation of the link 101 as the element 110 moves in the direction of the arrow 111. In this manner, the contact force and direction on the contacting surfaces between the element 110 and the surface 113 of the link 101 as well as between the element 110 and the surface 112 of the device structure 102 can be controlled as is done in the design of cam and follower surfaces.
(44) It is also appreciated by those skilled in the art that the element 110 of the inertial igniter 100 of FIG. 6a-6e and electrical G-switches 150 of FIGS. 7a-7d and 8a-8c may be provided with a spring 190 (shown in dashed lines in FIG. 6a) to provide a preloading force on the element 110 for the purpose of assisting the aforementioned centrifugal force that tends to move it in the direction of the arrow 111 as the device spins about the axis 109 (in which case, the spring 190 is preloaded in compression). A preloading of the spring 190 in tension would provide a force that counters the centrifugal force that tends to move it in the direction of the arrow 111 as the device spins about the axis 109.
(45) It is also appreciated by those skilled in the art that the stop 104 may be positioned such that any desired angle 191 (FIG. 6a) of the link 101 from its aforementioned singular position (shown in FIG. 6c), i.e., from the line 115, can result. As a result, the amount of counterclockwise rotation that the link 101 has to undergo before it passes its singular position and activate the device can be controlled. As a result, and particularly by providing the element 110 with a spring 190 that is preloaded in compression, the spin rate at which the device is activated can be reduced.
(46) It is also appreciated by those skilled in the art that with a compressively preloaded spring 190, the amount of torque (moment of the force applied by the element 110 to the link 101 about the pin joint 103) required to rotate the link counterclockwise to its said singular position (FIG. 6c) is determined by the opposing torques that the springs 105 and 190 apply to the link 101. As a result, for a given device, by increasing the level of compressive preloading of the spring 190, the tensile preloading of the spring 105 can be increased for a given device activation spin rate. As a result, the potential energy stored in the spring 105 increased, thereby increasing the kinetic energy of the striker link 101 as the pyrotechnic components 106 and 114 impact. This capability of the inertial igniter embodiment 100 and G-switch embodiment 150 is particularly important in applications in which the spin rate of the munitions using these devices is relatively low.
(47) It is also appreciated by those familiar with the art that by moving the attachment point 107 of the spring 105 to the device structure 102 to the right or to the left, the amount of counterclockwise rotation of the link 101 that is required to bring it to its new aforementioned singular position is changed. For example, by moving the attachment point 107 to the right, the angle is increased (the line 115 is rotated counterclockwise, thereby increasing the angle 191 of the link 101 to the line 115, i.e., to its singular position).
(48) The spin rate that is required to achieve activation of the inertial igniter 100 of FIG. 6a-6e and electrical G-switches 150 of FIGS. 7a-7d and 8a-8c can be varied by varying the inertia and geometry of the element 110, the angles between the surface 112 of the structure 102 of the device and the surface 113 of the link 101 as seen in the schematic of FIG. 6a. In addition, the said surfaces 112 and 113 as well as the contacting surfaces of the element 110 may be formed as curved to achieve the desired levels of counterclockwise rotation of the link 101 as the element 110 moves in the direction of the arrow 111. In this manner, the contact force and direction on the contacting surfaces between the element 110 and the surface 113 of the link 101 as well as between the element 110 and the surface 112 of the device structure 102 can be controlled as is done in the design of cam and follower surfaces.
(49) With a compressively preloaded spring 190, the amount of torque required to rotate the link counterclockwise to its said singular position (FIG. 6c) is determined by the opposing torques that the springs 105 and 190 apply to the link 101. As a result, for a given device, by increasing the level of compressive preloading of the spring 190, the tensile preloading of the spring 105 can be increased for a given device activation spin rate. As a result, the potential energy stored in the spring 105 increased, thereby increasing the kinetic energy of the striker link 101 as the pyrotechnic components 106 and 114 impact. This capability of the inertial igniter embodiment 100 and G-switch embodiment 150 is particularly important in applications in which the spin rate of the munitions using these devices is relatively low.
(50) Another embodiment 300 of the present inertia igniter invention is shown in the schematic of FIG. 9a. In this embodiment, the striker component of the inertial igniter 300 is the striker link 301, which is attached to the structure of the inertial igniter 302, by a pin joint indicated with numeral 303. A spring 305, which can be preloaded in tension, is attached to the structure of the inertial igniter 302 on the end 306 and to the striker link 301 on the other end 307, preferably with pin or pin-like joints. In its pre-activation state shown in FIG. 9a, the striker link 301 is pressed (such as near its tip 308) against a rotating link 309, through an intermediate ball 310. The link 309 is attached to the structure of the inertial igniter 302 via a rotary joint 311, which allows it to rotate about the axis 312. The axis 312 is parallel to the plane of view of FIG. 9a, thereby allowing the link 309 to rotate up or down relative to the plane of the rotation of striker link 301. A mass 317 is attached to the tip of the link 309. The mass 317 may be required to be added if the center of mass of the link 309 is not on the side of the striker link 301 or if it is relatively low to properly operate the inertial igniter as described later in this disclosure. The latter becomes particularly the case when the setback acceleration level is relatively low. The elements 313 and 314, fixed to the striker link 301 and the inertial igniter structure 302, respectively, are the two components of the ignition pyrotechnic. Alternatively, a one piece pyrotechnic element may be used, in which case the element 313 can be the ignition impact mass or pin and the element 314 can be the one piece impact initiated pyrotechnic element.
(51) In general, a relatively shallow “dimple” 315 is provided on the surface of the striker link 301 to seat the ball 310 so that the ball 310 is prevented from sliding out from between the link 309 and the striker link 301. The tensile force applied to the striker link 301 is seen to generate a torque that tends to rotate the striker link 301 in the counterclockwise direction, thereby pressing the ball 301 against the surface of the link 309. The link 309 can be provided with a stop 316 under it as shown in FIG. 9a (or above the ball 310 contact side of the link 309) to prevent its ball contacting end from significantly moving up and loose contact with the ball 310. The link 309 is also provided with a biasing compressive spring 331 shown in the side view “A” of FIG. 9c, which tends to rotate its ball contacting end up, thereby pressing its opposite end against the stop 316. In practice, the spring 331 can be a torsion spring.
(52) The inertial igniter 300 is intended to be initiated by setback acceleration, which is considered to be in the direction perpendicular to the plane of the rotation of the striker link 301 (the plane of the FIG. 9a) and directed upwards (outward from the said plane of the rotation of the striker link 301). In particular, the inertial igniter 300 is intended to be initiated by setback accelerations that are either relatively low level or are relatively short in duration or both relatively low level and relatively short duration. In such applications, the setback acceleration is not long enough in duration to actuate a release mechanism, which is required for safety reasons to prevent accidental initiation, as well as accelerate a striker mass long enough to provide it with enough mechanical energy to achieve ignition of pyrotechnic materials of the inertial igniter upon the previously described pyrotechnic impact (between a two part pyrotechnic components, a pin impacting a one-part pyrotechnic material, a pin impacting a percussion cap, or the like).
(53) The operation of the embodiment 300 is as follows. At rest, the tip 308 of the striker link 301 is pressed against the link 309 through the ball 310 by the tensile force of the preloaded spring 305 acting on the striker link 301 as can be seen in the schematic of FIG. 9a. When the munitions using the inertial igniter 300 is fired, the setback acceleration (in the direction of the arrow 330 shown in FIG. 9c, which is perpendicular to the plane of the inertial igniter 300, i.e., the plane of FIG. 9a) will cause the mass 317 to be pushed down. As the tip of the link 309 (with the mass 317) moves down, the surface of the link 309 that is in contact with the ball 310 slides pass the ball 310, and when it has moved down enough and passed the ball 310, it is designed to have also moved passed the bottom surface of the striker link 301, thereby clearing the striker link 301 to be released. In FIG. 9c, the positions of the link 309 and mass 317 after the application of said setback acceleration and its said downward motion to clear the striker link 301 is shown in dashed lines and indicated by the numeral 332. The tensile force of the spring 305 will then accelerate the striker link 301 rotationally in the counterclockwise direction until the pyrotechnic components 313 and 314 impact and cause ignition. The latter state of the striker link 301 is shown in FIG. 9b. The flames and sparks generated by the ignition of the pyrotechnic material 313 and 314 is then routed out from provided ports, usually through a hole such as the hole 318 to below the base to initiate the thermal material pyrotechnics. In some applications, the generated flames and sparks are required to be routed from the side or from the top (opposite to the direction of exit from the hole 318) side of the inertial igniter 300.
(54) It is appreciated by those skilled in the art that the inertial igniter 300 can still operate without the use of the intermediate ball 310 being present between the striker link 301 (such as near the tip 308) and the rotating link 309. However, the inertial igniter 300 can be constructed with such an intermediate rolling element to minimize the friction forces between the striker link 310 and the rotating link 309. In general, it is desired that the friction forces be as small as possible so that the (downward) force that the setback acceleration needs to generate while acting on the inertia (mass 317) to rotate the rotating link 309 down to release the striker link 301 is minimized. By minimizing the required downward setback acceleration generated force, the inertia of the required mass 317, i.e., the size of the required mass 317, is minimized.
(55) It is appreciated by those skilled in the art that the aforementioned biasing (torsion) spring of the link 309 is selected such that in the case of accidental drops or other similar accidental (no-fire) events, the link 309 is not rotated downwards enough for the link 309 to clear the ball 310, i.e., to release the striker link 301.
(56) It is also appreciated by those skilled in the art that the spring 305 may be a compressive spring preloaded in compression in the configuration of the inertial igniter shown in the schematic of FIG. 9a. Such a compressively preloaded spring 305 needs to be positioned above the striker link 301 as viewed in the schematic of FIG. 9a, so that it would apply a preloading counterclockwise torque to the striker link 301 which would allow the inertial igniter 300 to operate as previously described for the tensile spring 305. Alternatively, the spring 305 may be a torsion spring, which can be positioned at the pin joint 303, and preloaded in the clockwise direction so that in the configuration shown in the schematic of FIG. 9a, it would apply a counterclockwise torque to the striker link 301 which would allow the inertial igniter 300 to operate as previously described for the tensile spring 305.
(57) It is also appreciated by those familiar with the art that in an alternative embodiment of the inertial igniter 300, FIG. 9a, the rotating link 309 may be replaced by a translating element 320, as shown in the FIG. 9d of the appropriately modified side view “A” of FIG. 9a. In this alternative embodiment, the link 309 and its rotary joint 311 are replaced with the translating element 320, which is designed to translate in the guide 321 (sidewalls of the guide to prevent lateral displacement of the translating element 320 not shown for clarity—the guide may also be provided with friction reducing coated surfaced and/or rolling elements such as balls or rolling needles—not shown), which is in turn attached to the inertial igniter structure 302. The translating element 320 is also provided with a compressive biasing spring 322, which at rest would keep the translating element 320 in the configuration shown in solid lines against the stop 323. As was previously described for the embodiment of FIG. 9a, the tensile force applied to the striker link 301 by the spring 305 generates a torque that tends to rotate the striker link 301 in the counterclockwise direction, thereby pressing the ball 301 against the surface of the translating element 320. In its pre-activation state shown in FIG. 9a, the striker link 301 is pressed (preferably near the tip 308) against the translating element 320, through an intermediate ball 310, FIG. 9d. Depending on the level of setback acceleration, i.e., if it is relatively low, then the mass of the translating element 320 may have to be increased by increasing its size and/or material density.
(58) The inertial igniter 300 embodiment with the translating element 320 is still intended to be initiated by setback acceleration, which is considered to be in the direction of the arrow 330 shown in FIG. 9d. In particular, the inertial igniter is similarly intended to be initiated by setback accelerations that are either relatively low level or are relatively short in duration or both relatively low level and relatively short duration. In such applications, the setback acceleration is not long enough in duration to actuate a release mechanism, which is required for safety reasons to prevent accidental initiation, as well as accelerate a striker mass long enough to provide it with enough mechanical energy to achieve ignition of pyrotechnic materials of the inertial igniter upon the previously described pyrotechnic impact (between a two part pyrotechnic components, a pin impacting a one-part pyrotechnic material, a pin impacting a percussion cap, or the like).
(59) The operation of the inertial igniter 300 embodiment with the translating element 320 is as follows. At rest, the tip 308 of the striker link 301 is pressed against the translating element 320 through the ball 310 by the tensile force of the preloaded spring 305 acting on the striker link 301 as can be seen in the schematic of FIG. 9a. When the munitions using the inertial igniter is fired, the setback acceleration (in the direction of perpendicular to the plane of the inertial igniter 300, i.e., the plane of FIG. 9a) will act on the inertia of the translating element 320 (and the mass 324—if present), causing the translating element 320 to travel down. As the translating element 320 moves down, the surface of the translating element that is in contact with the ball 310 slides pass the ball 310, and when it has moved down enough and passed the ball 310, it is designed to move passed the bottom surface of the striker link 301, thereby clearing the striker link 301 to be released. The latter position of the translating element 320 is shown in dashed line in FIG. 9d and with numeral 324. The tensile force of the spring 305 will then accelerate the striker link 301 rotationally in the counterclockwise direction until the pyrotechnic components 313 and 314 impact and cause ignition, FIG. 9a. The latter state of the striker link 301 is as shown in FIG. 9b for the inertial igniter 300 with the rotating release link 309. The flames and sparks generated by the ignition of the pyrotechnic material 313 and 314 is then routed out from provided ports, usually through a hole such as the hole 318 to below the base to initiate the thermal material pyrotechnics. In some applications, the generated flames and sparks are required to be routed from the side or from the top (opposite to the direction of exit from the hole 318) side of the inertial igniter 300.
(60) It is appreciated by those skilled in the art that the inertial igniter 300 can also operate without the use of the intermediate ball 310 being present between the striker link 301 (preferably near the tip 308) and the translating element 320. However, the inertial igniter 300 is preferably constructed with such an intermediate rolling element to minimize the friction forces between the striker link 310 and the translating element 320. In general, it is desired the said friction forces be as small as possible so that the (downward) force that the setback acceleration needs to generate while acting on the inertia of the translating element 320 to translate the translating element 320 down to release the striker link 301 is minimized. By minimizing the said required downward setback acceleration generated force, the inertia of the translating element 320, i.e., the size of the resulting device is also reduced.
(61) It is appreciated by those skilled in the art that the aforementioned compressive biasing spring 322 is selected such that in the case of accidental drops or other similar accidental (no-fire) events, the translating element 320 is not translated downwards enough to clear the ball 310, i.e., to release the striker link 301.
(62) The inertial igniter 300 can also be readily modified to operate as a so-called electrical G-switch upon activation by the aforementioned all-fire setback acceleration and thereby close (open) a normally open (closed) electrical circuit. The construction and operation of the electrical G-switch is identical to those of the inertial igniter 300 of FIGS. 9a-9d, except that the pyrotechnic components 313 and 314 of the inertial igniter 300 are replaced by contact and circuit closing (opening) elements described below.
(63) In one embodiment of the resulting electrical G-switch, the pyrotechnic component 314 of the inertial igniter 300 (FIG. 9a) is replaced with the contact element 151 (as shown in FIG. 7a and the close-up view “A” of FIG. 7b1) and its pyrotechnic component (or striker pin) element 313 by the contact bridging element 152 (as shown in FIG. 7a and the close-up view “B” of FIG. 7b2). All other elements of the resulting G-switch are identical to those of the inertial igniter 300 of FIG. 9a.
(64) The contact element 151, replacing the pyrotechnic component 314 of the inertial igniter 300 (FIG. 9a) and the close-up view “A” of which is shown in the schematic of FIG. 7b1, is similarly fixed to the structure 302 of the resulting electrical G-switch.
(65) The contact element 152, replacing the pyrotechnic component 313 of the inertial igniter 300 (FIG. 9a) and the close-up view “B” of which is shown in the schematic of FIG. 7b2, is similarly fixed to the striker link 301 of the resulting electrical G-switch.
(66) It is also appreciated by those skilled in the art that all alternative features and methods of construction and operation described for the electrical G-switch 150 of FIG. 7a may also be applied to the present electrical G-switch resulting from the inertial igniter 300.
(67) The resulting electrical G-switch operates in a manner similar to the inertial igniter 300 of FIGS. 9a-6b, i.e., as a result of the all-fire setback acceleration, the tip of link 309 that engages the tip 308 of the link 301 via the intermediate ball 310 is pushed down, thereby releasing the striker link 301 as was previously described for the inertial igniter 300. The tensile force of the spring 305 will then accelerate the striker link in the counterclockwise direction until the contact strip 164 of the contact element 152 (close-up view “B” of FIG. 7b2) comes into contact with the contacts 153 and 154 of the contact element 151 (close-up view “B” of FIG. 7b2) as shown in the schematic of FIG. 7d for the G-switch 150. As a result, the wires 155 and 156 are connected electrically, and the circuit to which they are connected is closed.
(68) It is appreciated by those skilled in the art that similar to the electrical G-switch 150 of FIGS. 7a-7d, more than two contacts 153 and 154 may be provided on the contact element 151, thereby allowing the electrically conductive strip 164 of the contact element 152 to close more than one electrical circuit (when using pairs of contacts 153 and 154 and electrically isolated electrically conductive strips 164 on the contact elements 151 and 152, respectively) or allowing at least three contacts (similar to contacts 153 and 154) on the contact element 151 to form a junction by an electrically conductive strip 164.
(69) It is appreciated by those skilled in the art that as was described for the electrical G-switch 150 of FIG. 7a, the electrical G-switch resulting from the inertial igniter 300 may be designed for opening an already closed electrical circuit by replacing the pair of contact elements 151 and 152 shown in FIGS. 7b1 and 7b2, for example by the alternative contact elements 171 and 172, respectively, which are shown in the close-up views “C” and “D” in the schematics of FIGS. 8a and 8b. The G-switch will then operate as was described for the 150 of FIG. 7a.
(70) It is also appreciated by those familiar with the art that all alternative designs and variations that were previously described for the G-switch embodiment 150 of FIG. 7a may also be applied to the present G-switch embodiment resulting similarly from the inertial igniter 300 of FIG. 9a and its disclosed variations.
(71) It is appreciated by those familiar with the art that spinning rounds are fired in rifled barrels so that as the round is accelerated along the length of the barrel to the desired barrel exit velocity, the round is also accelerated rotationally (about its long axis) to the desired barrel exit spin rate. Hereinafter, the rotational acceleration about the long axis of the round (i.e., the spin axis) is referred to as the “spin acceleration”, and the spin acceleration corresponding to the all-fire setback acceleration experienced by the round during firing is referred to as the “all-fire spin acceleration”.
(72) In another embodiment, a method for constructing inertial igniters that utilizes the aforementioned all-fire spin acceleration to initiate pyrotechnic materials of the igniter is described together with examples of such inertial igniter designs. These all-fire spin acceleration activated inertial igniters are intended to stay inactive, i.e., do not initiate, when subjected to axial acceleration (even the setback acceleration) and rotary accelerations that are not along the long axis of the round.
(73) Such “all-fire spin acceleration” activated inertial igniters have a very important safety advantage over inertial igniters that are activated by setback acceleration. This safety advantage results from the fact that during acceleration drops, even from relatively high heights, e.g., from the aforementioned heights of 40 feet, that could result in accelerations of up to 18,000 Gs with durations of up to 1 msec, can only induce spin acceleration levels that are a very small fraction of the round all-fire spin acceleration levels. As a result, such inertial igniters are particularly suitable from the safety point of view for the so-called spinning rounds, i.e., those rounds that are fired by rifled barrels to achieve (usually high) spin rates, sometimes of the order of magnitude of several hundred spins per second.
(74) One representative embodiment 350 of such “all-fire spin acceleration” activated inertial igniter is shown in the schematic of FIG. 10. In this embodiment, the striker component of the inertial igniter 350 is the rotary striker 351, which is attached to the structure of the inertial igniter 352, by a pin joint indicated with numeral 353. The tip 354 of a relatively elastic beam element 355 or the like, which is attached to the structure of the inertial igniter 352, is positioned to engage mating groove 356 of a groove providing portion 357 attached (such as being integral) to the tip 358 of the rotary striker 351. The elements 359 and 360, fixed to the rotary striker 301 and the inertial igniter structure 352, respectively, are the two components of the ignition pyrotechnic. Alternatively, a one piece pyrotechnic element may be used, in which case the element 359 is preferably the ignition impact mass or pin and the element 360 is preferably the one piece impact initiated pyrotechnic element. The inertial igniter 350 is intended to be initiated by the aforementioned firing setback acceleration induced (all-fire) spin acceleration, which is considered to be in the direction by the arrow 361 in FIG. 10.
(75) In general, a stop 362 which is attached to the inertial igniter structure 352 is provided to prevent the clockwise rotation of the rotary striker 351, FIG. 10.
(76) The operation of the embodiment 350 is as follows. At rest, and its pre-activation configuration, the tip 354 of the elastic beam 355 engages the groove 356 of the groove providing portion 357 attached to the tip 358 of the rotary striker 351. As a result, the elastic beam 355 provides resistance to the rotational motion of the rotary striker 351 about the pin joint 353 as shown in the schematic of FIG. 10. When the munitions using the inertial igniter 350 is fired by a gun, the setback acceleration and the barrel rifling forces the round to be also accelerated rotationally about the long axis of the round, i.e., causes the round to be subjected to an all-fire spin acceleration, in the direction of the arrow 361, noting that the direction of the firing acceleration is intended to be perpendicular to the plane of the FIG. 10 and outward from the plane.
(77) When the round is fired, as the setback acceleration and thereby the spin acceleration (in the direction of the arrow 361—i.e., clockwise direction) of the round structure (to which the inertial igniter structure 352 is attached) is increased, the essentially stationary rotary striker 351 begins to be accelerated in the same clockwise direction by the engaging elastic beam 355. The clockwise acceleration of the rotary striker 351 acts on the moment of inertia of the rotary striker 351, generating a resisting (dynamic reaction) torque. The resisting torque in turn needs to be generated by a force applied by the engaging elastic beam 355 to the rotary striker 351 tip 358 at the groove 356. As a result, the elastic beam begins to deflect in bending (downward as seen in the schematic of FIG. 10), until the clockwise acceleration being applied to the rotary striker 351 is large enough to cause enough deflection of the tip 354 of the elastic beam 355 to free the rotary striker 351 from engagement with the elastic beam 355. From this moment of disengagement of the rotary striker 351 from the elastic beam 355, the inertial igniter structure 352 continues to spin accelerate in the clockwise direction (direction of the arrow 361). As a result, pyrotechnic component 360 is accelerated towards the pyrotechnic component 359, until they impact and cause ignition. The flames and sparks generated by the ignition of the pyrotechnic material 359 and 360 are then routed out from provided ports, usually through a hole such as the hole 363 in the inertial igniter structure 352 below its base to initiate the thermal material pyrotechnics. In some applications, the generated flames and sparks are required to be routed from the side or from the top (opposite to the direction of exit from the hole 363) side of the inertial igniter 350.
(78) The length of the engaging tip 354 inside the groove 356 and the stiffness of the elastic beam 355 determine the level of torque that the rotary striker 351 needs to apply to the elastic beam 355 to disengage it from the said elastic beam (following certain amount of—preferably elastic—bending deformation of the elastic beam 355), i.e., the level of spin acceleration at which the rotary striker 351 is released. This level is generally desired to be relatively high for safety reasons, i.e., to prevent inertial igniter activation during accidental drops as previously discussed. The level of spin acceleration at which the rotary striker 351 is released is also desired to be relatively high so that to increase the relative speed of the pyrotechnic components 359 and 360 at the time of their impact to ensure ignition reliability.
(79) It is appreciated by those familiar with the art that a number of elastic element types known in the art may be used instead of the elastic beam 355 to perform the same function, i.e., accelerate the rotary striker 351 in the clockwise direction to certain desired release acceleration level (generally significantly below the all-fire spin acceleration levels) before releasing the rotary striker 351. Alternative methods of achieving the same goal can also be achieved using a connecting element 381 to connect the tip 358 of the rotary striker 351 to the inertial igniter structure 352 as shown in FIG. 15. The connecting element 381, in this case a shearing pin, is then designed to fail (i.e., break) to shear and release the rotary striker 351 at the desired spin acceleration level. In general, the shear pin 381 can be provided with a notch 382 to concentrate shearing stress in that section of the shear pin 381 to achieve more controlled shearing at the desired spin acceleration level.
(80) Another alternative method of achieving rotary striker release at the desired spin acceleration level is the use of a detent pin 385 as shown in the schematic of FIG. 16. The detent pin 385 is attached to the inertial igniter structure 352 and its locking ball 386, which is biased forward by the preloaded compressive spring 387, engages the dimple 388 provided on the tip 358 of the rotary striker 351. The size of the detent ball and the depth of the dimple and its preloading spring would then determine the level of acceleration at which the rotary striker 351 is released during the firing.
(81) In addition, the elements (such as the elastic element 355) providing the aforementioned resisting torque may be positioned at the rotary joint 353, and may be of a torsion spring type.
(82) It is noted that the center of mass of the rotary striker 351, FIG. 10, can be located along the axis of rotation of the rotary joint 353. By such positioning of the center of mass of the rotary striker 351, any accidental acceleration (in the axial or lateral directions or rotational accelerations about axes perpendicular to the spin axis), even very high axial or lateral accelerations caused by drops from aforementioned high heights causing linear accelerations of up to 18,000 Gs with duration of up to 1 msec, would not cause a torque about the spin axis (the axis of the rotary joint 353) of the rotary striker 351, therefore would not cause the inertial igniter 350 to be initiated.
(83) The inertial igniter 350 can also be readily modified to operate as a so-called electrical G-switch upon activation by the aforementioned all-fire (setback acceleration induced) spin acceleration, and thereby close (open) a normally open (closed) electrical circuit. The construction and operation of the electrical G-switch is identical to those of the inertial igniter 350 of FIG. 10, except that the pyrotechnic components 359 and 360 of the inertial igniter 350 are replaced by contact and circuit closing (opening) elements described below.
(84) In one embodiment of the resulting electrical G-switch, the pyrotechnic component 360 of the inertial igniter 350 (FIG. 10) is replaced with the contact element 151 (as shown in FIG. 7a and the close-up view “A” of FIG. 7b1) and its pyrotechnic component (or striker pin) element 359 by the contact bridging element 152 (as shown in FIG. 7a and the close-up view “B” of FIG. 7b2). All other elements of the resulting G-switch are identical to those of the inertial igniter 350 of FIG. 10.
(85) The contact element 151, replacing the pyrotechnic component 360 of the inertial igniter 350 (FIG. 10) and the close-up view “A” of which is shown in the schematic of FIG. 7b1, is similarly fixed to the structure 352 of the resulting electrical G-switch.
(86) The contact element 152, replacing the pyrotechnic component 359 of the inertial igniter 350 (FIG. 10) and the close-up view “B” of which is shown in the schematic of FIG. 7b2, is similarly fixed to the rotary striker 351 of the resulting electrical G-switch.
(87) It is also appreciated by those skilled in the art that all alternative features and methods of construction and operation described for the electrical G-switch 150 of FIG. 7a may also be applied to the present electrical G-switch resulting from the inertial igniter 350.
(88) The resulting electrical G-switch operates in a manner similar to the inertial igniter 350 of FIG. 10, i.e., when the round is fired, as the setback acceleration and thereby the spin acceleration in the direction of the arrow 361 (clockwise direction) of the round structure to which the inertial igniter structure 352 is attached is increased, the essentially stationary rotary striker 351 begins to be accelerated in the same clockwise direction by the engaging elastic beam 355. The said clockwise acceleration of the rotary striker 351 acts on the moment of inertia of the rotary striker 351, generating a resisting (dynamic reaction) torque. The said resisting torque in turn needs to be generated by a force applied by the engaging elastic beam 355 to the rotary striker 351 tip 358 at the groove 356. As a result, the elastic beam begins to deflect in bending (downward as seen in the schematic of FIG. 10), until the said clockwise acceleration being applied to the rotary striker 351 is large enough to cause enough deflection of the tip 354 of the elastic beam 355 to free the rotary striker 351 from engagement with the elastic beam 355. The inertial igniter structure 352 will then continues to spin accelerate in the clockwise direction (direction of the arrow 361). As a result, the contact element 151 is accelerated towards the contact element 152, until the contact strip 164 of the contact element 152 (close-up view “B” of FIG. 7b2) comes into contact with the contacts 153 and 154 of the contact element 151 (close-up view “B” of FIG. 7b2) as shown in the schematic of FIG. 7d for the G-switch 150. As a result, the wires 155 and 156 are connected electrically, and the circuit to which they are connected is closed. The resulting electrical G-switch is preferably provided with a biasing tensile spring 364, which is attached to the rotary striker 351 on one end and the inertial igniter structure 352 on the other end, preferably by pin joints 365 and 366, respectively, as shown in the schematic of FIG. 10. The presence of the biasing tensile spring 364 ensures that once the contacts 151 and 152 come into contact as is described above, they will stay in contact.
(89) It is appreciated by those skilled in the art that similar to the electrical G-switch 150 of FIGS. 7a-7d, more than two contacts 153 and 154 may be provided on the contact element 151, thereby allowing the electrically conductive strip 164 of the contact element 152 to close more than one electrical circuit (when using pairs of contacts 153 and 154 and electrically isolated electrically conductive strips 164 on the contact elements 151 and 152, respectively) or allowing at least three contacts (similar to contacts 153 and 154) on the contact element 151 to form a junction by an electrically conductive strip 164.
(90) It is also appreciated by those skilled in the art that as was described for the electrical G-switch 150 of FIG. 7a, the electrical G-switch resulting from the inertial igniter 350 may be designed for opening an already closed electrical circuit by replacing the pair of contact elements 151 and 152 shown in FIGS. 7b1 and 7b2, for example by the alternative contact elements 171 and 172, respectively, which are shown in the close-up views “C” and “D” in the schematics of FIGS. 8a and 8b. The G-switch will then operate as was described for the 150 of FIG. 7a.
(91) It is also appreciated by those familiar with the art that all alternative designs and variations that were previously described for the G-switch embodiment 150 of FIG. 7a may also be applied to the present G-switch embodiment resulting similarly from the inertial igniter 350 of FIG. 10 and its disclosed variations.
(92) The inertial igniter embodiments 100, 300 and 350 shown in the schematics of FIGS. 6, 9 and 10, respectively, and all their indicated variations can be packaged in a relatively rigid housing, such as in the cylindrical package 400 shown in the isometric view of FIG. 11, which can consist of a top cap 401, sidewall 402 and base 403. In general and to make the packaged inertial igniter 400 small, the base 403 (or cap 401) and/or sidewall 402 of the housing can be integral to the structure 102, 302 and 352 of the inertial igniter embodiment 100, 300 and 350 shown in the schematics of FIGS. 6, 9 and 10, respectively. In the isometric view of FIG. 11, the inertial igniter flame exit port 404 is shown to be located on the base 403 of the packaged inertial igniter 400, to allow the flame 405 to exit and initiate the thermal battery in which the packaged inertial igniter is assembled.
(93) The inertial igniter 300 is intended to be initiated by setback accelerations that are either relatively low level or are relatively short in duration or both relatively low level and relatively short duration. In such applications, the setback acceleration is not long enough in duration to actuate a release mechanism, which is required for safety reasons to prevent accidental initiation, as well as accelerate a striker mass long enough to provide it with enough mechanical energy to achieve ignition of pyrotechnic materials of the inertial igniter upon the previously described pyrotechnic impact (between a two part pyrotechnic components, a pin impacting a one-part pyrotechnic material, a pin impacting a percussion cap, or the like).
(94) The inertial igniter 350 is intended to be initiated by setback acceleration induced spin acceleration in spinning rounds (fired by guns with rifled barrels). When center of mass of the rotary striker 351 is located on its axis of rotation (along its rotary joint axis), then no linear (axial or lateral) accelerations or rotational accelerations along axes perpendicular to the spin axis will not initiate the inertial igniter. Therefore the inertial igniter will be safe when dropped from very high heights such as 40 feet that can cause linear accelerations of the order of 18,000 G with up to 1 msec duration.
(95) It is appreciated by those familiar with the art that the inertial igniter housing may be any shape instead of the cylindrical shape as shown in the isometric view of FIG. 11. In addition, the flame exit port may be located almost anywhere on the inertial igniter housing, including the side 402 or the top cap 401, depending on where the igniter pyrotechnic material is located and how it is guided to exit for proper initiation of the thermal battery pyrotechnics.
(96) In certain applications, the thermal battery is required to be initiated under all-fire condition with an extremely high level of reliability, for example, a reliability of even better than 99.999% at 95% confidence level. In such situations, even if an inertial igniter is designed and fabricated for very high initiation reliability under all-fire condition, it might not be capable of satisfying such extremely high reliability level requirements. In addition, even if an inertial igniter is expected to be reliable to such extremely high levels, the process of proving such reliability levels requires extensive and extremely costly testing procedures. For these reasons, it is highly desirable to provide such thermal batteries with at least two, independently activated, inertial igniters to make it possible to achieve such extremely high thermal battery initiation reliability using inertial igniters with significantly lower proven reliability levels that can be achieved at significantly lower costs. The isometric view of FIG. 12 shows such an assembly 420 (indicated by numerals 421) of three packaged inertial igniters 400 over a common base 422.
(97) It is also appreciated by those familiar with the art that the G-switch embodiment 150, formed from the inertial igniter embodiment 100 of FIG. 6, as well as the G-switches that can be similarly formed as described previously in this disclosure from the inertial igniter embodiments 300 and 350 of FIGS. 9 and 10, respectively, including all their indicated variations, can be packaged in a relatively rigid housing as shown in the isometric view of FIG. 13 and indicated by the numeral 450. Such a housing 451 may, for example, be cylindrical in shape with the G-switch sealed within the housing to protect its elements from environmental effects. The G-switch housing may also be in any shape instead of the cylindrical shape of FIG. 13. The at least two contact wires 452 and 453 may, for example, be brought out from the base of the G-switch packaging 450. Alternatively, the at least two contact tab elements or pins (not shown) commonly used in electronic components may be used for mounting of the G-switch on circuit boards or the like as is common practice in the electronics industry.
(98) In general and to make the packaged G-switch 450 small, the housing can be integral to the structure 102, 302 and 352 of the inertial igniter embodiment 100, 300 and 350 shown in the schematics of FIGS. 6, 9 and 10, respectively, which are used to construct the indicated G-switches.
(99) It is appreciated by those familiar with the art that similar to the multiple inertial igniter assembly of at least two inertial igniters shown in FIG. 12, two or more G-switches 450 may also be assembled and used to significantly increase the reliability with which the resulting G-switch assembly can detect all-fire condition. An example of an isometric view of such an assembly 470 of three G-switches 471 over a common base 472 is shown in FIG. 14.
(100) In one alternative embodiment of the G-switch assembly 450, at least one of the G-switches of the assembly may be used to detect accidental drops, particularly accidental drops from very high height, such as drops from heights of up to 40 feet that can result in impact shocks of up to 18,000 Gs with up to 1 msec of duration. Similarly, other at least one G-switches may be used to detect shock loadings due other accidental drops or nearby explosions. As a result, the resulting G-switch assembly can be used to differentiate all-fire conditions from almost all no-fire conditions, even drops from very high heights.
(101) While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.
