Mechanical inertial igniters for reserve batteries and the like for munitions

Abstract

A device including: an impact mass movably restrained relative to a base; and a release mechanism configured to be movable between a restrained position for preventing movement of the impact mass and a released position for permitting movement of the impact mass when the release mechanism is subjected to an acceleration greater than a predetermined magnitude and duration; wherein the release mechanism having a release mass movable when subjected to the acceleration, the movement of the release mass not being influenced by movement of the impact mass.

Claims

1. A device comprising: an impact mass movably restrained relative to a base; and a release mechanism configured to be movable between a restrained position for preventing movement of the impact mass and a released position for permitting movement of the impact mass when the release mechanism is subjected to an acceleration greater than a predetermined magnitude and duration the release mechanism having a release mass movable when subjected to the acceleration; wherein the release mechanism is configured such that a force is not applied from the impact mass to the release mass when the impact mass is subjected to the acceleration.

2. The device of claim 1, wherein the release mass is separated from the impact mass in a lateral direction relative to a direction of the acceleration.

3. The device of claim 1, wherein the impact mass is rotatably movable relative to the base.

4. The device of claim 1, further comprising a flame producing means for outputting a flame upon movement of the impact mass.

5. The device of claim 4, wherein the flame producing means comprises: a first protrusion provided to protrude from a surface of the impact mass; a second protrusion provided to protrude from the base, the second protrusion being positioned such that movement of the impact mass causes contact between the first and second protrusions; a pyrotechnic provided proximate to one of the first and second protrusions such that the contact between the first and second protrusions ignites the pyrotechnic; and an opening in the base for outputting the flame from the base.

6. The device of claim 1, further comprising a biasing member for biasing the impact mass in a direction opposite to the direction of the acceleration.

7. The device of claim 1, further comprising a circuit for one of opening or closing an electrical circuit upon movement of the impact mass.

8. The device of claim 7, wherein the circuit comprises: an electrically conductive member provided to a surface of the impact mass; and first and second electrical contacts, electrically isolated from each other, provided to the base, the first and second electrical contacts being positioned such that movement of the impact mass causes the electrically conductive member to contact and close the electrical circuit between the first and second electrical contacts.

9. The device of claim 7, wherein the circuit comprises: an electrically non-conductive member provided to protrude from a surface of the impact mass; and first and second electrical contacts, electrically connected to each other, provided to the base, the first and second electrical contacts being biased in an electrically closed position and movable to an electrically open position, the first and second electrical contacts being positioned such that movement of the impact mass causes the electrically non-conductive member to move the first and second electrical contacts to the electrically open position.

10. The device of claim 1, wherein the release mechanism comprises: a shaft having one end engaged with a portion of the impact mass and an other end engaged with the release mass, the shaft being movable to the released position upon movement of the release mass when the release mass is subjected to the acceleration; and a shaft biasing element for biasing the shaft into the released position when the release mass moves and is no longer engaged with the other end of the shaft.

11. The device of claim 10, further comprising a release mass biasing element for biasing the release mass into a position of engagement with the other end of the shaft.

12. The device of claim 10, wherein the release mass moves in translation.

13. The device of claim 10, wherein the release mass moves in rotation.

14. The device of claim 1, further comprising a housing including the base.

15. A method for moving an impact mass upon the impact mass experiencing an acceleration greater than a predetermined magnitude and duration, the method comprising: movably restraining the impact mass relative to a base; moving a release mechanism between a restrained position for preventing movement of the impact mass and a released position for permitting movement of the impact mass when the release mechanism is subjected to the acceleration; configuring the release mechanism to have a release mass movable when subjected to the acceleration, wherein the release mechanism does not apply a force to the release mass when the impact mass is subjected to the acceleration.

16. The method of claim 15, further comprising separating the release mass from the impact mass in a lateral direction relative to a direction of the acceleration.

17. The method of claim 15, further comprising outputting a flame upon movement of the impact mass.

18. The method of claim 15, further comprising one of opening or closing an electrical circuit upon movement of the impact mass.

19. The method of claim 15, wherein the release mass moves in translation.

20. The method of claim 15, wherein the release mass moves in rotation.

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 of the prior art.

(3) FIG. 2 illustrates an isometric cut away view of an inertial igniter assembly of the prior art.

(4) FIG. 3 illustrates a full isometric view of the prior art inertial igniter of FIG. 2.

(5) FIG. 4 illustrates a schematic of a cross-section of the first inertial igniter embodiment of the present invention.

(6) FIG. 5 illustrates a schematic of a cross-section of the second inertial igniter embodiment of the present invention.

(7) FIG. 6A illustrates a schematic of a cross-section of the third inertial igniter embodiment of the present invention.

(8) FIG. 6B illustrates the view A of the release mechanism of the embodiment of FIG. 6A.

(9) FIG. 7 illustrates a schematic of a cross section of a normally open g-switch embodiment corresponding to the first inertial igniter embodiment of FIG. 4.

(10) FIG. 8 illustrates a schematic of a cross section of a normally open g-switch embodiment corresponding to the second inertial igniter embodiment of FIG. 5.

(11) FIG. 9 illustrates a schematic of a cross section of a normally open g-switch embodiment corresponding to the third inertial igniter embodiment of FIG. 6A.

(12) FIG. 10 illustrates a schematic of a cross section of a normally closed g-switch embodiment corresponding to the first inertial igniter embodiment of FIG. 4.

(13) FIG. 11 illustrates a schematic of a cross section of a normally closed g-switch embodiment corresponding to the second inertial igniter embodiment of FIG. 5.

(14) FIG. 12 illustrates a schematic of a cross section of a normally closed g-switch embodiment corresponding to the third inertial igniter embodiment of FIG. 6A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(15) A schematic of a cross-sectional view of a first embodiment 50 of an inertia igniter is shown in FIG. 4. The inertial igniter 50 consists of a base element 51, which in a thermal battery construction shown in FIG. 1 can be positioned in a housing (10 in FIG. 1) with the base element 51 positioned on the top of the thermal battery cap (19 in FIG. 1). However, the base element 51 can also be a portion of the housing. A striker mass 52 (alternatively referred to as a impact mass) of the inertial igniter 50 is attached to the base element 51 via a rotary joint 53. Although shown as being rotatable, the striker mass 52 can also be movable in translation, such as in the direction opposite to the direction of arrow 63. In such configuration, the striker mass can be on one or more rails for constraining the translation along a direction of the one or more rails and the one or more rails can include bearings or other low friction means, such as treated low friction surfaces between the one or more rails and corresponding bores in the striker mass 52.

(16) A post 54, which is fixed to the base element 51 is provided with a hole 55. A shaft 57 is positioned in the hole 55 and is movable within the hole from a position engaging the striker mass 52 to a position not engaging the striker mass 52. Attached to the shaft 57 is the head 59 which in the pre-initiation configuration shown in FIG. 4 rests against a sliding member 58 (alternatively referred to as a release mass). A compressively preloaded compressive spring 72 is also provided between the head 59 of the shaft 57 and a surface 73 of the post 54 to keep the head 59 in contact with the sliding member 58.

(17) In the configuration of FIG. 4, the (up-down) sliding member 58 is shown to block the movement of the shaft 57 and head 59 member away from engagement with the striker mass 52 (the release mechanism is engaged with the mass 52 in a restrained position). Thereby in the configuration of FIG. 4, an end 60 of the shaft 57 is positioned below a tip 61 of the striker mass 52, preventing the striker mass 52 from rotating clockwise in the direction of the arrow 62 as shown in FIG. 4.

(18) The sliding member 58 is free to slide down against a member 68, if necessary via rolling elements 69. However, sliding contact between the member 68 and sliding member 58 may also be utilized, particularly if the contacting surfaces are low friction surfaces. However, it will be appreciated by those skilled in the art that the rolling elements 69 would provide a means of reducing sliding friction between the sliding member 58 and the member 68 and minimize the possibility of stiction between the moving surfaces. As a result, a level of force needed to move the sliding member down become highly predictable, which in turn makes the level of acceleration needed to release the inertial ignite striker mass 52 more predictable as is described later. Similar roller elements (not shown) may also be positioned between the contacting surfaces of the sliding member 58 and the head 59 of the shaft 57. The rolling elements 69 can be housed in retaining cavities (not shown) in the sliding member 58 or similarly held onto the sliding member 58 via a commonly used cage element (not shown).

(19) The member 68 is fixed to the base element 51. A spring element 70 resists downward motion of the sliding member 58, and can be preloaded in compression so that if a downward force that is less than the compressive preload is applied to the sliding member 58, the applied force would not cause the sliding element 58 to move downwards. A stop 71 fixed to the member 68, is provided to allow the spring element 70 to be preloaded in compression by preventing the sliding member 58 from moving further up (in the direction of arrow 68) from the configuration shown in FIG. 4.

(20) During the firing, the inertial igniter 50 is considered to be subjected to setback acceleration in the direction of the arrow 63. The acceleration in the direction of the arrow 63 acts on the inertia of the sliding element 58 and generates a downward force that tends to slide the sliding element 58 downwards (opposite to the direction of acceleration). The compression preloading of the spring element 70 is generally selected such that with the no-fire acceleration levels, the inertia force acting on the sliding element 58 would not overcome (or at most be equal to) the preloading force of the spring element 70. As a result, the inertial igniter 50 is ensured to satisfy its prescribed no-fire requirement. Alternatively, and particularly when the peak no-fire acceleration level is higher than the peak all-fire (setback) acceleration levels but is very short duration as compared to the duration of the all-fire acceleration, then the time that it takes for the sliding element 58 to move down enough to clear the head 59 of the shaft 57 is designed to be less than the duration of the no-fire acceleration events.

(21) Now if the acceleration level in the direction of the arrow 63 is high enough, then the aforementioned inertia force acting on the sliding element 58 will overcome the preloading force of the spring element 70, and will begin to travel downward. If the acceleration level is applied over a long enough period of time (duration) as well, i.e., if the all-fire condition is satisfied and the sliding element 58 will have enough time to travel down far enough and clears the head 59 of the shaft 57, then the compressively preloaded spring 72 would push the head 59 and the shaft 57 away from the striker mass 52, thereby disengaging the tip 60 of the shaft 57 from the tip 61 of the striker mass 52. As a result, the striker mass 52 is released and is allowed to be accelerated in the clockwise rotation as indicated by the arrow 62 (the release mechanism takes a release portion where it is no longer engaged with the mass 52). As a result, for a properly designed inertial igniter 50 (i.e., by selecting a proper mass and moment of inertial for the striker mass 52 and the range of clockwise rotation for the striker mass 52 so that it would gain enough energy), the striker mass 52 will gain enough kinetic energy to initiate the pyrotechnic material 64 between the pinching points provided by the protrusions 65 and 66 on the base element 51 and the bottom surface of the striker mass 52, respectively, as shown in FIG. 4. The ignition flame and sparks can then travel down through the opening 67 provided in the base element 51. When assembled in a thermal battery similar to the thermal battery 16 of FIG. 1, the inertial igniter is mounted in the housing 10 such that the opening 67 is lined up with the opening 12 into the thermal battery 11 to activate the battery by igniting its heat pallets.

(22) It will be appreciated by those skilled in the art that the duration of the all-fire acceleration level can also be important for the operation of the inertial igniter 50 by ensuring that the all-fire acceleration level is available long enough to accelerate the striker mass 52 towards the base element 51 to gain enough energy to initiate the pyrotechnic material 64 as described above by the pinching action between the protruding elements 65 and 66.

(23) It will be appreciated by those skilled in the art that when the inertial igniter 50 (FIG. 4) is assembled inside the housing 10 of the thermal battery assembly 16 of FIG. 1, a cap 18 (or a separate internal capnot shown) is commonly used to secure the inertial igniter 50 inside the housing 10. In such assemblies, the stop element 71 is no longer functionally necessary since the sliding element 58 can be prevented from being pushed upward by the force of the spring element 70 and releasing the striker mass 52 by an internal surface/component of the cap. It will be, however, appreciated by those skilled in the art that by providing the stop element 71, particularly if it is extended to at least partially over the top surface of the striker mass 52, then the storage of the inertial igniter 50 and the process of assembling it into the housing 10 is significantly simplified since one does not have to provide secondary means to keep the spring element 70 from pushing the sliding element 58 further up and thereby clearing the head 59 of the shaft 57 and releasing the striker mass 52.

(24) It will be appreciated by those skilled in the art that in the inertial igniter embodiment 50 of FIG. 4, and in contrast to the prior art of FIGS. 2 and 3, the downward force due to the acceleration in the direction of the arrow 63 acting on the mass (inertia) of the striker mass 52 does not increase the level of force that is required for the slider element 58 to be moved downward to release the striker mass as was previously described. It will also be appreciated by those skilled in the art that in the inertial igniter of the prior art shown in FIGS. 2 and 3, as the inertial igniter 200 is accelerated similarly in the direction of the arrow 218, the generated force due to the mass of the striker element 205 would cause the locking balls 207 to be forced outward against the surfaces of the pockets 212 of the collar 211, thereby increasing the resistance of the collar to downward motion, thereby to the release of the striker element 205. This very important feature of the inertial igniter embodiment 50 of FIG. 4 ensures the consistency with which the igniter striker mass 52 can be released within a very narrow range of acceleration in the direction of the arrow 63, i.e., for the case of munitions, within a narrow range of firing setback or the like acceleration event.

(25) It will also be appreciated by those skilled in the art that by providing a preloaded compressive force level in the spring 72 that is greater than the maximum friction and stiction forces between the tip 61 of the striker mass 52 and the tip 60 of the shaft 57 as well as between the shaft 57 and the hole 55 in the post 54, then once the sliding element 58 has cleared the head 59 of the shaft 57, then the tip 60 of the shaft 57 is ensured to be pulled away from the top 61 of the striker mass 52 to initiate its accelerated clockwise rotation in the direction of the arrow 62, thereby initiating the pyrotechnic material 64 as was previously described.

(26) In the embodiment of FIG. 4, the sliding element 58 and the spring element 70 of the release mechanism of the inertial igniter 50 may be configured in numerous ways, e.g., the sliding element 58 may be replaced with a rotating member (which may further reduce friction and stiction in the release mechanism) and the spring member 70 may be integral with the resulting rotating member, i.e., as a flexible beam element with living joints with the inertia of the beam acting as the mass element of the resulting slider element.

(27) It will be appreciated by those skilled in the art that the hole 55 and the cross-section of the mating shaft 57 do not have to be circular. For example, the designer may choose to use non-circular shapes instead to provide the means of preventing and/or minimizing the rotation of the shaft 57 about its long axis. For example, the designer may choose a trapezoidal mating shape or a shape close to or similar to a trapezoidal shape so that during assembly the two parts could be mated only in the correct orientation and thereby eliminate assembly mistakes and the need for post assembly inspection.

(28) In certain applications, the all-fire setback acceleration level is either not high enough to impart enough kinetic energy to the striker mass 52 or its duration is not long enough to allow the striker mass be released by the downward motion of the sliding element 58 and the clockwise rotation of the striker mass in the direction of the arrow 62. As a result, the striker mass 52 is released as a result of setback firing acceleration or other prescribed acceleration events, but the striker mass is not capable to reliably ignite the pyrotechnic material 64 by the resulting impact (pinching) between the protruding elements 65 and 66. In such applications, additional kinetic energy may be provided by the potential energy stored in appropriately positioned preloaded spring element(s). An example of such an inertial igniter is shown in the schematic of the cross-sectional view of the inertial igniter embodiment 80 of FIG. 5.

(29) All components of the inertial igniter embodiment 80 of FIG. 5 are identical to those of the embodiment 50 of FIG. 4, except for the following added components. The same components illustrated in FIGS. 4 and 5 are similarly numbered, however, such reference numerals are omitted in FIG. 5 for the sake of clarity. In the embodiment 80, the embodiment 50 of FIG. 4 is provided to add sides 74 and 75 and a top cover 76 to the base element 51 to form a housing. A compressively preloaded spring 77 is also positioned between the top cover 76 and the top surface 78 of the striker mass 52. Then, as the inertial igniter 80 is subjected to the firing setback acceleration or the like in the direction of the arrow 63, and if the aforementioned prescribed all-fire conditions have been satisfied, then following the release of the striker mass 52 as was previously described for the embodiment 50 of FIG. 4, the continuing acceleration in the direction of the arrow 63 and/or the force exerted by the compressively preloaded spring 77 will rotationally accelerate the striker mass 52 in the clockwise direction as shown by the arrow 62 in FIG. 4, imparting enough kinetic energy to the striker mass 52 so that as the resulting impact (pinching) between the protruding elements 65 and 66 would cause the pyrotechnic material 64 to ignite.

(30) A third embodiment 90 of the inertial igniter of the present invention is shown in the cross-sectional view of FIG. 6A. All components of the inertial igniter embodiment 90 of FIG. 6A are identical to those of the embodiment 50 of FIG. 4, except for the slider element 58 based striker mass release mechanism. In the embodiment 90 of FIG. 6A, the sliding element 58 is replaced by a rotating mechanism to reduce device complexity and the sliding friction forces. In the embodiment 90, the motion of the head 59 of the shaft 57 away from the striker mass engagement, FIGS. 4 and 6A, is prevented by the surface 81, the opposite side of the end 85 of the link 82 shown in the view A of FIG. 6B. The link 82 is attached to the inertial igniter base 51 via the rotary joint composed of the supports 83 and the rotary joint pin 84 as shown in FIG. 6A and the view A shown in FIG. 6B. The link 82 is also provided with a preloaded spring 86 which is biased to keep the link 82 against the stop (for example stop 87, which is fixed to the post 54, FIG. 6A, or the stop 88, which is fixed to the rotary joint support 83, FIG. 6B). The link stop (elements 87 or 88) is positioned such that in pre-initiation configuration, the biasing preloaded spring 86 would position the end 85 of the link 82 against the head 59 of the shaft 57.

(31) Then when the inertial igniter is accelerated in the direction of the arrow 63, the force resulting by the action of the acceleration on the mass of the link 82 and its end 85 will tend to rotate the link 82 in the clockwise direction as seen in the view A of FIG. 6B. If the level of acceleration in the direction of the arrow 63 is high enough to overcome the preloaded force of the spring 86, then the link 82 will begin to rotate in the clockwise direction as seen in FIG. 6B. If the duration of the above acceleration is long enough, then the link 82 will rotate in the clockwise direction enough for the surface 81 of the end 85 of the link 82 to clear the head 59 of the shaft 57, thereby allowing the shaft 57 to move away from engagement with the striker mass 52, thereby allowing the striker mass to accelerate downward as was described for the embodiment of FIG. 4 and cause the pyrotechnic material 64 of the inertial igniter to be ignited.

(32) It will be appreciated by those skilled in the art that the link 82 may be fixedly attached to the base plate 51 and be provided with a rotary (flexural) living joint to serve the same purposed as is described above for the link 82 and its end 85. In such an arrangement, the flexibility of the said flexural living joint may be used to serve the purpose of the spring 86. In which case the aforementioned preloading of the spring 86 may also be achieved by designing the flexural element such that in normal conditions the link 82 positions the end 85 passed the head 59 of the shaft 57. Then the prescribed preloading level is achieved by rotating the link in the clockwise direction and bringing it to stop against the provided stop element (elements 87 or 88 in FIG. 6A).

(33) In the embodiments 50, 80 and 90 of FIGS. 4, 5 and 6A, respectively, pyrotechnic materials 64 are shown to be used for ignition upon inertial igniter initiation through the impact (pinching) between the protruding elements 65 and 66. It is, however, appreciated by those skilled in the art that instead of the pyrotechnic material 64, which has to be applied individually to the inertial igniter 50 base 51 over the protruding element 65, one may instead install commonly used percussion caps such as those commonly used in gun bullets or the like in a provided cavity (not shown but usually specified by the percussion cap manufacturer) in the base 51 (to be initiated by the impact of the appropriately shaped protruding element 66). The advantage of using the pyrotechnic material 64 is that they can be designed to initiate at impact energies that are significantly lower than that of percussion primers, however at significantly higher per unit cost. Percussion primers are however mass produced at high volumes and are therefore significantly lower in cost and easy to install. For purposes of this disclosure and the appended claims, pyrotechnic material will include the use of the pyrotechnic materials as discussed above with regard to FIGS. 4, 5 and 6A as well as the alternative percussion caps discussed immediately above.

(34) In the above embodiments, the disclosed devices are intended to actuate, i.e., release their striker mass 52 in response to an all-fire acceleration level to accelerate downwards to impact the provided pyrotechnics materials causing them to ignite. The same mechanisms used for the release of the striker mass due to an all-fire acceleration can be used to provide the means of opening or closing an electrical circuit, i.e., act as a so-called G-switch, that is actuated only if it is subjected to an all-fire acceleration profile, while staying inactive during all no-fire conditions, even if the acceleration level is higher than the all-fire acceleration level but significantly shorter in duration. As a result, this novel G-switch device would satisfy all no-fire (safety) requirements of the device in which it is used while activating in the prescribed all-fire condition.

(35) Schematics of such G-switches are shown in FIGS. 7-12, where FIGS. 7-9 illustrate a normally open G-switch corresponding to the inertial igniter configurations of FIGS. 4, 5 and 6A, respectively, and FIGS. 10-12 illustrate a normally closed G-switch corresponding to the inertial igniter configurations of FIGS. 4, 5 and 6A, respectively.

(36) Turning first to the G-switch 100 of FIG. 7, which is similar to the inertial igniter illustrated in FIG. 4, except that its pyrotechnic material and initiation elements (elements 64, 65 and 66 in FIG. 4) are removed. An element 106, which is constructed of an electrically non-conductive material is fixed to the base 51 of the device as shown in FIG. 7. The element 106 is provided with two electrically conductive elements 104, 107 with contact ends 103 and 109, respectively. Electrical wires 105 and 108 are in turn attached to the electrically conductive elements 104 and 107, respectively. As it was described for the embodiment 50 of FIG. 4, when the device is subjected to an all-fire acceleration in the direction of arrow 63, the striker mass 52 is release and rotated about the pivot 53 in the direction of arrow 62. The striker mass 52 is provided with a flexible strip of electrically conductive material 101 which is fixed to the bottom surface of the striker mass 52 (such as by being soldered or attached with fasteners 102). Therefore, as the striker mass 52 rotates towards the base 51 of the device, it would cause the flexible electrically conductive strip 101 to come into contact with the contact ends 103, 109, thereby causing the circuit through the wires 105 and 108 to close.

(37) As discussed above with regard to FIG. 5, the g-switch of FIG. 7 can be provided with a biasing spring 77 to ensure that the flexible electrically conductive strip 101 stays in contact with the contact ends 103 and 109. Such an embodiment is shown in the g-switch 110 of FIG. 8.

(38) As also discussed above with regard to FIGS. 6A and 6B, the sliding element 58 can be replaced by a rotating mechanism to reduce device complexity and the sliding friction forces. Such an embodiment is shown in the g-switch 120 of FIG. 9.

(39) The G-switch 100 of FIG. 7 can also be readily modified to provide a normally close switching configuration. As an example, the contact components of the G-switch 130 may be modified to that shown in the schematic of FIG. 10. This embodiment 130 of the G-switch has all its other components being the same as those of the embodiment 100 of FIG. 10. The normally closed G-switch 130 is provided with two flexible contact elements 133 and 135, which are fixed to the electrically non-conductive member 134, which is fixed to the base 51 of the device 130. The flexible contact elements 133 and 135 are provided with contact points 131 and 137, which are normally in contact (such as by being biased towards each other), thereby causing the wires 132 and 136 that are attached to the contact elements 133 and 135 to close the electrical circuit to which they are connected. The striker mass 52 is provided with a non-conductive member 138 as shown in FIG. 10.

(40) As was described for the embodiment 100 of FIG. 7, when the device is subjected to an all-fire acceleration in the direction of arrow 63, the striker mass 52 is release and rotated about the pivot 53 in the direction of arrow 62. As the non-conductive member 138 reaches the contact points 131 and 137, the force of the acceleration acting on the inertia of the striker mass 52 causes the member 138 to be inserted between the contact points 131 and 137, thereby rendering their contacts open and opening the aforementioned electrical circuit to which the wires 132 and 136 are connected.

(41) As discussed above with regard to FIG. 5, the g-switch of FIG. 10 can be provided with a biasing spring 77 to ensure that the member 138 stays inserted between the contact points 131 and 137. Such an embodiment is shown in the g-switch 140 of FIG. 11.

(42) As also discussed above with regard to FIGS. 6A and 6B, the sliding element 58 can be replaced by a rotating mechanism to reduce device complexity and the sliding friction forces. Such an embodiment is shown in the g-switch 150 of FIG. 12.

(43) 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.