EP1847795A2

EP1847795A2 - Pointing device inertial isolation and alignment mounting system

Info

Publication number: EP1847795A2
Application number: EP07106475A
Authority: EP
Inventors: John M. Shipman; Daniel E. Burkholder; Richard L. Bissell
Original assignee: Honeywell International Inc
Current assignee: Honeywell International Inc
Priority date: 2006-04-19
Filing date: 2007-04-19
Publication date: 2007-10-24
Also published as: EP1847795A3; US20100269681A1

Abstract

An inertial isolation and alignment system (100) for a sensitive component or apparatus affixed to a mortar barrel (120) comprising a barrel clamp assembly (200) which supports two parallel bearing rail followers (210) and pointing device cage assembly (300) which supports two parallel linear bearing rails (340). The bearing rail followers (210) and linear bearing rails (340) form a sample sliding contact linear motion bearing system. The bearing rail followers (210) on the barrel clamp assembly (200) allow the cage assembly (300) to slide freely along the length of the linear bearing rails (340). During firing, the travel vector is decoupled from the cage assembly (300) by the bearing rail followers (210) as they move with the barrel (120) along the linear bearing rails (340) leaving the cage assembly (300) suspended in inertial space. The cage assembly (300) then accelerates under the force of gravity over the distance of the displaced travel of the bearing rail followers (210) back to its rest position landing on dampers (360), each fastened to the front end of a linear bearing rail (340).

Description

The present patent application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Serial No. 60/793,169 , which was filed April 19, 2006. The full disclosure of U.S. Provisional Patent Application Serial No. 60/793,169 is incorporated herein by reference.
This 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.
During 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 fool-pounds (500k 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 white 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 120mm 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. Patent 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. Patent No. 6,814,179 , uses shock isolators that are comprised of rubber and polyurethane foam to absorb shock and vibration.
The 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.

In the Drawings:

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:

Figure 1 is a perspective view of the preferred inertial isolation and alignment assembly mounted on a mortar weapon;
Figure 2 is a perspective view of the preferred inertia isolation and alignment assembly of Figure I in the extended position;
Figure 3 is a perspective view of the preferred inertial isolation and alignment assembly of Figure I in the ready-to-fire position;
Figures 4A and 4B are front and side views of the preferred barrel clamp assembly;
Figures 5A and 5B are front and side views of the preferred cage assembly;
Figure 6 shows the preferred inertial isolation and alignment assembly in the pre-fire condition; and
Figure 7 shows the preferred inertial isolation and alignment assembly immediately after a firing condition.

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. Fig. 1 shows a perspective view of inertial isolation and alignment assembly 100, affixed to a mortar weapon comprising a base plate 110, mortar barrel 120, and bipod 130. The inertial isolation and alignment assembly 100 is affixed to the underside of mortar barrel 120. As can be seen, inertial isolation and alignment assembly 100 consists of a barrel clamp assembly 200 to secure inertial isolation and alignment assembly 100 to mortar barrel 120, and a cage assembly 300 to encase a pointing device 310, such as a TALIN^™ pointing device.
Fig. 2 depicts a perspective view of the preferred inertial isolation and alignment assembly 100 in the extended position. The first part of this embodiment is barrel clamp assembly 200 which mounts to mortar barrel 120. Barrel clamp assembly 200 includes bearing rail followers 210, which position linear bearing rails 340 parallel to mortar barrel 120. The second part of this embodiment is cage assembly 300, which encases pointing device 310 and anchors linear bearing rails 340. The top surface 212 and bottom surface 214 of bearing rail followers 210, in combination with the linear bearing rails 340, form the basis of the sliding contact linear motion bearing system, similar to the slide actions of semi-automatic rifles or pistols.
Fig. 3 shows a perspective view of the preferred inertial isolation and alignment assembly 100 of Fig. 1 in the ready-to-fire position. It illustrates how linear bearing rails 340 of cage assembly 300 slide through bearing rail followers 210 of barrel clamp assembly 200, effecting the simple sliding contact linear motion bearing system.
Fig. 4A shows a front view of the preferred barrel clamp assembly 200, Barrel clamp assembly 200 comprises a saddle structure 220 and a saddle clamp structure 230 with saddle clamp bolts 240. Saddle structure 220 has saddle extensions 222 with bearing rail followers 210. Saddle structure 220 and saddle extensions 222 form a one piece "C" channel structure. However, saddle extensions 222 could also be separate mounting blocks permanently affixed to saddle structure 220. Saddle clamp structure 230 is affixed to saddle extensions 222 with saddle clamp bolts 240. Saddle extensions 222 are drilled and tapped from the top side at each corner to receive saddle clamp bolts 240. This entire saddle structure 220 is preferably machined from a solid piece of bar stock (such as 4340 steel, for example) to provide uniform strength and stress distribution throughout the structure. Saddle structure 220 can also be manufactured from aluminum, titanium, plastic, composite, or other materials able to withstand the forces exerted by a particular mortar weapon, and the temperature rise of the mortar barrel experienced during firing.
Barrel clamp assembly 200 is subjected to the acceleration and firing shock of more than two thousand g's on the 120mm 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.
Fig. 4B shows a side view of the preferred barrel clamp assembly 200. Saddle clamp structure 230 comprises two semi-circular shaped bands 232 with gusseted bolt eye extensions 234, which fit over mortar barrel 120 and bolt on both sides of saddle structure 220. Saddle clamp structure 230 also comprises a rigid mechanical connection 236, connecting the two saddle clamp bands 232, in order to assist in holding the alignment of inertial isolation and alignment assembly 100 constant. Rigid mechanical connection 236 can also function as a handle. The entire saddle clamp structure 230 is preferably machined from a solid piece of bar stock (such as 4340 steel, for example) to provide uniform strength and stress distribution throughout the structure. Saddle clamp structure 230 can also be manufactured from aluminum, titanium, plastic, composite, or other materials able to withstand the forces exerted by a particular mortar weapon, and temperature rise of the mortar barrel experienced during firing. Rigid mechanical connection 236 and saddle clamp bands 232 of the saddle clamp structure 230 can be three separate pieces bolted together, as long as the assembly maintains rigidity.
Fig. 5A shows a front view of the preferred cage assembly 300. The cage assembly 300 comprises side plates 320, base structure 330, linear bearing rails 340, shock isolators 350, and shock dampers 360. Base structure 330 comprises two side members 332, which are bolted to a base member 334 to form a u-sbaped shelf for mounting pointing device 310. Side plates 320 are fastened to shock isolators 350. Shock isolators 350 are also fastened to side members 332 of base structure 330. Base structure 330, shock isolators 350, and side plates 320 form an openended box for encasing pointing device 310. Linear bearing rails 340 are fastened to side plates 320, and shock dampers 360 are fastened to the front ends of linear bearing rails 340. Pointing device 310 is bolted onto base member 334 of base plate 330.
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.
Fig. 5B is a side view of the preferred cage assembly 300. Fasteners 322 connect side plates 320 to linear bearing rails 340. The fasteners 322 are preferably cap head socket screws, but are not limited to this type of fastener. Although Fig. 5B shows eight fasteners 322 attaching each of the linear bearing rails 340 to each of the side plates 320, this invention is not limited to eight fasteners, and other numbers of fasteners may be used.
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 120mm 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.
Figure 6 depicts the inertial isolation and alignment assembly 100 mounted on the underside of mortar barrel 120 while the mortar weapon is at rest prior to the initial firing. The initial installation of menial isolation and alignment assembly 100 is accomplished by bolting saddle clamp structure 230 to saddle structure 220 around mortar barrel 120 using saddle clamp bolts 240. Saddle clamp bolts 240 are tightened to a predetermined torque limit, such as 95 ft-lbs, for the 120mm mortar weapon, in a sequential pattern at 10 ft-lb, increments. Following proper installation of barrel clamp assembly 200 around mortar barrel 120, cage assembly 300 is installed by aligning linear bearing rails 340 with bearing rail followers 210, and sliding cage assembly 300 toward the base piste until it is resting on shock dampers 360, as shown in Fig. 6. This is the resdy-to-fire position.
Figure 7 depicts the extended position of the inertial isolation and alignment assembly 100. During a firing event, mortar barrel 120 recoils toward the base plate, causing barrel clamp assembly 200 to slide along linear bearing rails 340 of the inertial isolation and alignment assembly 100. At the end of the firing event, mortar barrel 120 comes to a stop, leaving case assembly 300 suspended on linear bearing rails 340 at a point equal to the distance the mortar barrel traveled during firing, as shown in Fig. 7. This is the extended position. The force of gravity then causes cage assembly 300 to slide down toward the base plate, and come to rest on the shock dampers 360 to the ready-to-fire position depicted in Fig. 6. This operation is repeated as many times as is required by the firing of the mortar weapon.
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

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 for removably affixing the inertial isolation and alignment assembly to the barrel;

a cage assembly affixed to the saddle clamp structure for encasing 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 inertialy isolate the cage assembly from the saddle structure.
The inertial isolation and alignment assembly of claim 1 wherein the saddle clamp structure comprises clamps.
The inertial isolation and alignment assembly of claim 1 wherein each of the at least two bearing rail followers is configured to accept the at least two linear bearing rails to form a sliding contact linear motion bearing system.
The inertial isolation and alignment assembly of claim 1 wherein each of the at least two bearing rail followers is configured to accept 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.
The inertial isolation and alignment assembly of claim 1 wherein the at least two linear bearing rails are affixed to the cage assembly.
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.
The inertial isolation and alignment assembly of claim 1 further comprising a quick release mechanism for the cage assembly.