Pointing Device Inertial Isolation and Alignment Mounting System
An inertial isolation and alignment system for a sensitive component or apparatus affixed to a mortar barrel comprising a barrel clamp assembly which supports two parallel bearing rail followers and pointing device cage assembly which supports two parallel linear bearing rails. The bearing rail followers and linear bearing rails form a simple sliding contact linear motion bearing system. The bearing rail followers on the barrel clamp assembly allow the cage assembly to slide freely along the length of the linear bearing rails. During firing, the travel vector is decoupled from the cage assembly by the bearing rail followers as they move with the barrel along the linear bearing rails leaving the cage assembly suspended in inertial space. The cage assembly then accelerates under the force of gravity over the distance of the displaced travel of the bearing rail followers back to its rest position landing on dampers, each on a linear bearing rail.
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The present patent application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Ser. No. 60/793,169, which was filed Apr. 19, 2006. The full disclosure of U.S. Provisional Patent Application Ser. No. 60/793,169 is incorporated herein by reference.
FIELDThis invention relates to large bore weapons and more particularly to a method and apparatus for isolating a shock from a mortar firing event while maintaining the alignment of a sensitive electronic pointing device for use on a mortar barrel or similar device.
BACKGROUNDDuring the firing of a large bore weapon a significant reaction force is imparted to the barrel and support structure. A support structure, which is required to travel a certain distance before absorbing the load, allows the barrel and its attached components to undergo a nearly instantaneous high-g acceleration. Sensitive electronic pointing devices, such as inertial measurement units (IMUs) or inertial navigation systems (INSs), and their attachment structures have been destroyed by this extreme acceleration and deceleration on occasion.
The present invention is a method and apparatus for isolating a sensitive electronic device from the barrel recoil travel using a linear motion bearing mounting system. For example, Honeywell's Tactical Advanced Land Inertial Navigator (TALIN™) pointing device requires a mortar mount assembly designed to provide a stable and protective cage parallel to the center line of the barrel. The mortar barrel of a 120 mm mortar weapon moves approximately twelve inches (12″) under a high acceleration, developing energy of approximately five hundred thousand foot-pounds (500 k ft-lbs.) and then decelerates to a stop in less than 0.010 seconds when fired from a base plate in a free standing configuration. More particularly, this mount needs to provide for the repeated firing of the mortar weapon without realignment or mechanical adjustment while maintaining a zero ballistic force vector on the pointing device.
Presently, typical PDMAs (pointing device mounting assemblies) cannot withstand the recoil acceleration force while attached to a 120 mm mortar barrel when fired. The typical PDMA experiences catastrophic failure of the steel mounting plates due to stress in excess of the bending moment of the material of their construction. This force exceeds the PDMA shock isolators' travel limit and transfers the shock load into the RLG (ring laser gyroscope) pointing device, causing internal physical damage.
Others have tried to solve the problem by designing a mounting platform for the RLG pointing device which allows the mortar barrel to recoil while separating the RLG pointing device from the recoil force through a shaft and sleeve bearing assembly. There is still hammer shock with this design, however, due to the loosely coupled parts. This design also lacks the durability desired for a PDMA.
A prior art device, described in U.S. Pat. No. 4,336,917, uses gas driven pistons and gas accumulator/controllers that are sensor-controlled to maintain position during shock and vibration. Another prior art device, described in U.S. Pat. No. 6,814,179, uses shock isolators that are comprised of rubber and polyurethane foam to absorb shock and vibration.
SUMMARYThe present invention solves the problem of inertial isolation by providing a mechanical assembly designed to provide a linear travel support frame constructed of bearing rail followers aligned parallel with the barrel reactive force vector and suspending the mass of the pointing device on linear bearing rails in a cage assembly that provides and maintains alignment while allowing the mortar weapon to accelerate and decelerate without transfer of motion to the suspended pointing device. The pointing device then returns to its rest position on the linear bearing mounting system by gravitational force. The parts work together to isolate the acceleration vector of the mortar barrel from the TALIN™ mass. During firing, the mortar barrel moves the attached bearing rail followers along the linear bearing rails, without imparting any acceleration to the cage assembly containing the TALIN™. The combined linear bearing rails and bearing rail followers form a simple sliding contact linear motion bearing system. During the mortar firing recoil, the force vector loads are directionally decoupled between the bearing rail followers and the linear bearing rails in their axis of travel. This prevents the mass of the RLG pointing device from inertially loading the cage assembly in excess of its out of plane deflection limits.
Various embodiments are described herein with reference to the following drawings. Certain aspects of the drawings are depicted in a simplified way for reason of clarity. Not all alternatives and options are shown in the drawings and, therefore, the invention is not limited in scope to the content of the drawings. In the drawings:
Disclosed is a preferred embodiment of an inertial isolation and alignment assembly 100 for mounting a sensitive component such as a pointing device to a mortar weapon, or the like.
Barrel clamp assembly 200 is subjected to the acceleration and firing shock of more than two thousand g's on the 120 mm mortar weapon during firing. This shock, coupled with torsional stress from a bolt down force of more than 95 foot-pounds across the diagonal length of barrel clamp assembly 200 and the temperature rise from repeated firings, requires additional structure for the barrel clamp assembly 200 to remain dimensionally stable.
Shock isolators 350 reduce the parallel and cross-axis firing shock on the pointing device during a firing event. The quantity and type of shock isolators 350 used is determined by the firing shock response spectrum from a particular mortar weapon and the spectral frequencies and magnitudes of attenuation required by the isolated mass. Shock isolators 350 are axially aligned with the center-of-mass of pointing device 310.
Shock dampers 360 are placed on the front ends of linear bearing rails 340. Shock dampers 360 provide reduced g-loads on the suspended pointing device cage assembly 300 as it returns to its rest position after a firing event. Shock dampers 360 may consist of air or hydraulic pistons. Shock dampers 360 may alternatively consist of springs or rubber material.
The length of linear bearing rails 340 is determined by the maximum amount of linear travel expected by the mortar barrel 120 during a firing event. In the case of the 120 mm mortar weapon, the typical travel distance required to seat the base plate in soft soil is approximately 12 inches, therefore the length of guide rails for this application would be approximately 20 inches.
As described above, cage assembly 300 is quickly installed by aligning linear bearing rails 340 with bearing rail followers 210 and sliding cage assembly 300 to the ready-to-fire position where it is resting on shock dampers 360. For the quick disconnect, the process is simply reversed. Cage assembly 300 is removed by sliding it from the ready-to-fire position beyond the extended position, until linear bearing rails 340 become free of bearing rail followers 210.
Although the invention has been described in detail with particular reference to a preferred embodiment, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above, are hereby incorporated by reference.
Claims
1. An inertial isolation and alignment assembly for aligning and isolating a shock of a sensitive component affixed to a barrel, the inertial isolation and alignment assembly comprising:
- a saddle clamp structure configured to removably affix the inertial isolation and alignment assembly to the barrel;
- a cage assembly affixed to the saddle clamp structure and configured to encase the sensitive component; and
- a linear motion bearing system comprising at least two linear bearing rails and at least two bearing rail followers, wherein the linear bearing rails and bearing rail followers cooperate to inertially isolate the cage assembly from the saddle structure, and wherein the at least two linear bearing rails are anchored to the cage assembly.
2. The inertial isolation and alignment assembly of claim 1, wherein the saddle clamp structure comprises clamps.
3. The inertial isolation and alignment of claim 1, wherein each of the at least two bearing rail followers is configured to accept a respective one of the at least two linear bearing rails to form a sliding contact linear motion bearing system.
4. The inertial isolation and alignment assembly of claim 1, wherein each of the at least two bearing rail followers is configured to accept a respective one of the at least two linear bearing rails so that each of the at least two linear bearing rails is substantially parallel to the mortar barrel.
5. (canceled)
6. The inertial isolation and alignment assembly of claim 1, further comprising shock dampers disposed at an end of each of the at least two linear bearing rails.
7. The inertial isolation and alignment assembly of claim 1, further comprising a quick release mechanism for the cage assembly.
8. A method for isolating a shock of a sensitive component affixed to a mortar barrel using an inertial isolation and alignment assembly, wherein the inertial isolation and alignment assembly comprises a saddle clamp structure configured to removably affix the inertial isolation and alignment assembly to the mortar barrel, a cage assembly affixed to the saddle clamp structure and configured to encase the sensitive component, and a linear motion bearing system, wherein the linear motion bearing system comprises at least two linear bearing rails and at least two bearing rail followers, wherein the linear bearing rails and bearing rail followers cooperate to inertially isolate the cage assembly from the saddle structure, and wherein the at least two linear bearing rails are anchored to the cage assembly, the method comprising:
- sliding the at least two linear bearing rails through the at least two bearing rail followers when a projectile is fired through the mortar barrel, thereby causing the cage assembly to be suspended in inertial space; and
- dampening a fall of the cage assembly.
9. The method of claim 8, the method further comprising affixing a saddle structure that contains the at least two bearing rail followers to the mortar barrel.
10. The method of claim 8, wherein each of the at least two bearing rail followers is configured to accept a respective one of the at least two linear bearing rails.
11. The method of claim 8, the method further comprising providing that the at least two linear bearing rails are substantially parallel to the mortar barrel.
12. The method of claim 8 wherein dampening comprises providing shock dampers.
13. The method of claim 8, the method further comprising releasing the cage assembly from the saddle structure when dismounting the sensitive component.
Type: Application
Filed: Feb 14, 2007
Publication Date: Oct 28, 2010
Applicant: Honeywell International Inc. (Morristown, NJ)
Inventors: John M. Shipman (Albuquerque, NM), Daniel E. Burkholder (Maurepas, LA), Richard L. Bissell (Rio Rancho, NM)
Application Number: 11/674,739
International Classification: F41A 23/00 (20060101);