Abstract:
An apparatus for securing movable elements of a multiple-axis drive mechanism with respect to the fixed base thereof during launch to prevent damage while unpowered. Mating surfaces of the lock secure the mechanism about all three axes of motion. Thus, the drives need to be only sufficiently designed to break free one element of the launch lock from the other element. Tapered or other guiding surfaces of the two elements of the launch lock make it self-aligning, such that mating surfaces are guided together once placed in sufficiently close proximity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/015,625, filed Dec. 20, 2007 entitled “MAGNETIC, LAUNCH LOCK APPARATUS AND METHOD” which application is hereby incorporated by reference herein in its entirety, including but not limited to those portions that specifically appear hereinafter, the incorporation by reference being made with the following exception: In the event that any portion of the above-referenced application is inconsistent with this application, this application supersedes said above-referenced application. U.S. patent application Ser. No. 11/770,666, filed Jun. 28, 2007, is hereby incorporated by reference herein in its entirety. 
     
    
     THE FIELD OF THE INVENTION 
       [0002]    This invention relates to mechanisms with multiple axes of motion, typically for aircraft and spacecraft applications and, more particularly, to novel systems and methods for locking such mechanisms during launch. 
       BACKGROUND 
       [0003]    Mechanisms with multiple axes, mounted and driven from a platform such as a satellite, are subject to acceleration forces during launch. Such mechanisms are typically not powered during launch, so some means must be employed to prevent damage. Mechanical latching systems are problematic in that they typically require additional drives, actuators, and controls as well as latches. They also introduce additional risk as another mechanism that may fail. They also require additional power. 
         [0004]    Many require human intervention, precise alignment, or both for pins, catches, and so forth to be set, or reset, for later removal by solenoids or other drives. Thus, it would be an advance in the art to provide a simple locking system that did not require additional motors or solenoids, high precision, or human intervention for securing during launch a mechanism and releasing it for operation thereafter. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    In view of the foregoing, an apparatus and method in accordance with the invention provide a magnetic lock relying on a magnet which may be electrically actuated, or a permanent magnet. A mating closure, such as a plate or other latching piece, configured, for example, as a plate or piloted, magnetically-retained cup, may be secured by the magnet with a force imposed by the magnet. Adjustment mechanisms to control a gap between the magnet and the closure may render the magnet&#39;s effective attraction force adjustable. A magnetic metal such as iron or a magnetic stainless may form a mount to receive the magnet and may direct magnetic flux. This mount or housing about the magnet may include an adjustment mechanism. The adjustment mechanism may control a gap between the magnet and the closure, or other constrained piece, in order to control magnet forces therebetween securing the lock. 
         [0006]    A self-piloting feature may be added by shaping the housing and the closure to taper and to have a resulting mating fit when closed. This configuration may also provide securement against displacement along or about all three principal, independent axes of motion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The foregoing features of the present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings in which: 
           [0008]      FIG. 1  is a perspective view of one embodiment of a multi-axis mechanism, in this case, a steering mirror assembly suitable for and tested with a magnetic lock in accordance with the invention; and 
           [0009]      FIG. 2  is one embodiment of a magnetic lock, as applied to securing the mirror structure of the apparatus of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0010]    In view of the foregoing, an apparatus and method in accordance with the invention provide electro-mechanical drivers to drive movement of an optical element (e.g., mirror, optics, focal plane, etc.) for aiming. 
         [0011]    Launch accelerations result in substantial reaction forces for all masses on board a launch vehicle. For example, a satellite containing a multi-axis mechanism includes masses that must be accelerated. Thus, under a launch acceleration, their inertia results in an inertial force that must be counteracted to prevent the hardware from displacing, colliding against other components, damaging drives, or the like. 
         [0012]    However, since the mechanism is not powered during launch, some means must be employed to prevent motion and damage. 
         [0013]    In one embodiment of an apparatus and method in accordance with the invention, a magnetic lock is designed to self-pilot, thus making alignment a very simple matter. Meanwhile, magnetic forces may be adjustable by controlling spacing between a magnet and a secured piece or element acting as a closure held thereby 
         [0014]    A housing, acting as a base or mount for a magnet, may double as a flux guide for the magnetic flux of the magnet. This is so even for a permanent magnet, by making a mount of a magnetic metal material. In one embodiment, the mount for the magnet may be formed with a taper, matched to a mating taper of the closure (secured piece held by the magnet). Thus the magnetic lock may be designed to self-pilot, making alignment a much simpler matter. The mating taper and closure also serve to prevent motion with respect to multiple axes. 
         [0015]    Referring to  FIG. 1 , an apparatus in accordance with the invention was implemented in a system  100  for stabilizing a fine steering mirror  102  or mirror  102 . In the illustrated embodiment a motor  104  served as the azimuth drive for the system  100 . Meanwhile, a mount  106  connected the movable element  12  rigidly to move with the mirror  102 . More details are included in U.S. patent application Ser. No. 11/770,666, filed Jun. 28, 2007. 
         [0016]    Sensors  14   a ,  14   b  were secured to a mount  108  that did not move with the mirror  102 . A yoke  110 , fixed to a turntable  112 , held a drive motor  116 . The mirror  102  was mounted on a flexible pivot member to rotate about a rotational axis  114 . The axis  114  could have been an axle, but was not in this case, in order to provide certain other mechanical and thermal benefits. 
         [0017]    Connected between the yoke  10  and the mirror  102  were the drive motor  116  and the flexible pivot system, in order to rotate or pivot the mirror  102  with respect to the yoke  110 , and turntable  112 , in the elevation direction. Meanwhile, the yoke  110  and  116  moved in the azimuth direction via the turntable  112  and the motor  104 . In the illustrated embodiment, a moveable element  12  operated as a segment of a circular or arcuate wedge  12  having a thickness that varied along its circumferential direction, the wedge  12  pivoting on an arm extending radially. The motor  104  caused the turntable  112  to rotate, which in turn caused mirror  102  to rotate in the azimuth direction. 
         [0018]    The performance parameters of pointing and stabilizing the mirror  102  of the system  100  demonstrated low energy use, excellent isolation for thermal and mechanical losses, negligible friction, and a very high repeatability and precision. 
         [0019]    Referring to  FIG. 2 , the system  100  was fitted with a magnetic launch lock  200 , in accordance with the invention. The housing of motor  104  may be thought of as fixed, or a fixed item with respect to the platform (e.g., satellite, rocket, aircraft) carrying the mirror  102 . Meanwhile, the mirror  102  is pivotably mounted with respect to the motor  104 , in order to be guided and driven in operation. 
         [0020]    Meanwhile, during launch, the mirror  102 , being unpowered in both axes may be damaged due to excessive motion cause by launch acceleration. 
         [0021]    In one embodiment of an apparatus and method in accordance with the invention, a lock  200  may secure the mirror  102  in fixed relation with respect to the motor  104 . 
         [0022]    In one embodiment, a lock  200  may include a magnet  202  secured inside or otherwise connected to a housing  204  or base  204 . The magnet  202  may be contained in a cup  212 , which is threaded into the housing  204 . The housing  204  may be configured to also act as a flux guide for the magnetic flux created by the magnet  202 . Accordingly, in certain embodiments the housing  204  may be manufactured of a suitable magnetic material, such as iron, magnetic stainless, or the like. 
         [0023]    The housing  204  may include a threaded cup  212  and a set screw  206  to position the magnet  202  with respect to the housing  204 . In one embodiment, the threaded cup  212  may act as the adjustment mechanism to move the magnet  202  to a particular position with respect to the housing  204 , the set screw  206  is then used to fix the position. In the illustrated embodiment, the magnet  202  is a right circular cylinder fitted to a housing  204  having an aperture sized to receive the magnet  202 . 
         [0024]    The housing  204  may include a pilot surface  208 . The pilot surface  208  may have a tapered, circular cross-section, a hemisphere, a taper of pyramidal shape, or the like. In the illustrated embodiment, the pilot surface  208  is conical, representing a frustum of a cone. As the conical pilot surface  208  ends at the edge  214 , where it meets the aperture in the housing  204 , a frustum is formed. 
         [0025]    The magnet  202  may be adjusted by the threaded cup  212  to extend out and away from the pilot surface  208 . However, in the illustrated embodiment, the magnet  202  is set within the aperture in the housing  204 , providing a setback  210  or air gap  210  (or simply a gap  210 ). Spacing the outer surface of the magnet  202  “down” into tile aperture, (e.g., below or inside the edge  214  of the pilot surface  208 ,where the pilot surface  208  meets the aperture of the housing  204 ), creates an air gap  210  but permits the housing  204  to still guide magnetic flux to tile closure  220 . Thus, as the magnet  202  retreats into the aperture or into the housing  204 , a decay in magnet force corresponds to the setback  210  from the surface of the magnet  202 , according to the laws of magnetism. 
         [0026]    In opposite, mating relation to the housing  204 , a closure  220  is secured to the mirror  102 . Actually, the housing  204  may be associated with the mirror  102  and the closure  220  may be associated with the base  104 . However, minimizing the mass and its moment of inertia on the moving mirror  102  improves the dynamic response of the system. 
         [0027]    A piloting surface  222  inside the closure  220  may be matched to fit in mating relation to the pilot surface  208  of the housing  204 . As a practical matter, the magnet  202  may itself be shaped. However, there is no need to do so. The housing  204  may be manufactured of a suitable magnetic material, responsive to magnetic flux and capable of extending the magnetic reach of the magnet  204 . Likewise, the closure  220  may be formed of a magnetic material similar to that of the housing  204 . 
         [0028]    In certain embodiments, the housing  204  may be fixed rigidly with respect to the motor  104 . Likewise, the closure  220  may be fixed rigidly to the mirror  102 , or a substrate thereof. Alternatively, a pre-determined amount of flexibility may be provided. Thus, the piloting surfaces  208 ,  222  may be able to be fitted more precisely. 
         [0029]    Alternatively, the housing  204  and closure  220  may be fitted together, with the magnet  202  in place. Any mounting hardware or brackets may be adjusted to ensure installation of the housing  204  and closure  220  with a suitably precise alignment. Thereafter, the movement of the mirror  102  toward the motor  104  may engage the closure  220  by the magnet  202  and its associated housing  204 . Meanwhile, the piloting surfaces  208 ,  220  engage one another, and come into a mating relationship, the magnet  202  providing the force to keep the closure  220  in proximity to the magnet  202 . 
         [0030]    In practice, controlling magnetic forces of permanent magnets is not a readily controllable design parameter, nor adjustable on site. Nevertheless, providing a setback  210  that can be arbitrarily adjusted by moving the magnet  202  requires only screwing the cup  212  and fixing it with the set screw  206 . Virtually any value of magnetic force available, up to a maximum capability of the magnet  202 , may be set. Thus, the air gap  210  or setback  210  may reduce the value of the magnetic force to an appropriate level. 
         [0031]    Typically, an appropriate level of magnetic force is a force less than the motive capability of the elevation drive driving the mirror  102  with respect to the azimuth motor  104 . The housing  204  may be oriented in such a way that the pilot surfaces  208 ,  220  support the actual forces due to launch acceleration. Thus, the launch lock  200  transfers the support of the mirror  102  through the lock  200 , and directly to the motor  104 . Those forces need not be supported by the drives of the mirror  102 . 
         [0032]    The mirror  102  is disengaged from the lock by movement, urged by the elevation drive, to draw the closure  220  axially away from the magnet  202  (axially with respect to the magnet  202  and housing  204 ). This action requires more force, than the actual stabilizing or holding force presented by the pilot surfaces  208 ,  220  during launch. 
         [0033]    Some of the advantages of the lock  200  in accordance with the invention include the lack of the need for an electrical circuit to maintain the force of the magnet  202 . An electromagnet may be used as a magnet  202 , but a permanent magnet functions adequately. The adjustment mechanism provides for a simple adjustment with a broad range of force available to design or calibrate the lock  200  to accommodate the forces available from the elevation drive of the mirror  102 . 
         [0034]    The system can also be locked again by using the elevation drive and azimuth drive to reposition the mirror  102  such that the pilot surfaces  208  and  222  are in close proximity, and then removing the power to the drives. 
         [0035]    Meanwhile, the lock  200  actually stabilizes the mirror  102  with respect to all three principal axes. Because the shape of the housing  204  resolves forces into its surfaces, the lock  200  may be oriented to support the launch loads in a direction transverse to the axis of symmetry of the magnet  202  and the housing  204 . Magnetic forces are augmented or leveraged by the orientation of the housing  204  and enclosure  220  with respective pilot surfaces  208 ,  222 . A properly designed orientation provides greater launch support than the actual magnet forces alone. 
         [0036]    In the illustrated embodiment, the force of the magnet  202  in the housing  204  was set to exceed the forces necessary to resist forces of launch accelerations. Meanwhile, the elevation drive for the mirror  102  was sized to exceed the effective force of the magnet  202  exerted to hold the closure  220  against the housing  204 . Various types of magnets may include neodymium-iron-boron magnets, samarium-cobalt magnets, or the like. 
         [0037]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.