Abstract:
The present invention provides an apparatus and methods directed to a selectively engageable shaft locking device. In one embodiment, a shaft lock device is presented which enables the testing of the shaft and shaft drive device without engaging the drive mechanism into a fully operational state. Another embodiment provides the ability to return the shaft lock device to a storage state after full engagement. The present invention also provides for methods of testing a selective shaft lock device according to the disclosures contained herein.

Description:
PRIORITY 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/044,351 filed Apr. 11, 2008 entitled “Selectively Engageable Shaft Lock and Drive Device.” This provisional patent application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to an improved shaft lock and drive device for use on aerodynamic surfaces. 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention relates to a selectively engageable shaft lock and drive device which can be used in applications such as steerable aerodynamic surfaces on rockets, missiles, bombs or the like. Typical shaft lock and drive devices in use have two states: a “storage” state in which the shaft and drive mechanism is locked in place and an “in use” state where the shaft lock is disengaged and the drive device operates to control the shaft and, in turn the connected aerodynamic surface. In typical shaft lock and drive devices currently in use, once the shaft lock is disengaged it cannot be returned to the “storage” or “engaged state.” This is primarily due to the fact that current shaft lock and drive devices typically use pyrotechnic bolts, fasteners or the like to engage the shaft lock. Once the pyrotechnic bolts are destroyed (as the shaft lock is disengaged), the shaft lock can never return to the “storage” or “engaged” state. 
         [0004]    Another problem addressed by the current invention relates to the inability of the prior art shaft lock and drive devices to be fully tested prior to deployment. The current invention provides for a reversible shaft lock and drive device which allows the drive device to be fully operated and tested while the rocket, missile, etc. is in a state other than flight. 
         [0005]    Another purpose of this invention is to provide a single mechanism to both maintain the shaft lock in the engaged position and to drive the shaft once the rocket, missile, etc. is in flight. This results in a fundamental cost and weight savings versus a separately operated device, regardless of type (motor, pyrotechnic, gas generator, etc.). 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description of the invention that follows may be better understood so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  illustrates an exploded view of an embodiment of the shaft lock device as contemplated by the present invention. 
           [0008]      FIG. 2  illustrates an embodiment of the shaft lock device according to the present invention in a “storage” state. 
           [0009]      FIG. 3  illustrates an embodiment of the shaft lock device according to the present invention in an “in use” or “testing” state. 
           [0010]      FIG. 4  illustrates an embodiment of the shaft lock device according to the present invention illustrating the use of a retraction device for bringing the shaft lock from an “in use” state to a “storage” state. 
           [0011]      FIG. 5  illustrates a close up view of the engagement structures according to an embodiment of the present invention in the “storage” state. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]      FIG. 1  illustrates an exploded view of a shaft lock device  10  according to the present invention. Fin  100  is attached to rotating fin shaft  110  such that a given rotation of shaft  110  causes fin  100  to rotate to a corresponding degree. Fixed buttress  120  is located in a fixed position along the axis of shaft  110  in order to provide a rigid surface against which stored energy device  130  can seat. In a preferred embodiment, fixed buttress  120  can have the shape of a ring, however other geometric shapes or devices (i.e., pins, etc.) are contemplated. Stored energy device  130  can be any type of mechanism capable of storing and releasing energy via compression, expansion or the like. In a preferred embodiment, stored energy device  130  is a spring. Slidable coupling  140  has a first major surface  142  and a second major surface  144 . Slidable coupling  140  is located along shaft  110  such that stored energy device  130  is disposed between slidable coupling  140  and fixed buttress  120  in a manner that stored energy device  130  can exert force against the first major surface  142  of slidable coupling  140  in a direction parallel to shaft  110 . Slidable coupling  140  is free to slide along shaft  110 , however the axial rotation of slidable coupling is inhibited via rotation lock  150 . Rotation lock  150  can be a spline, pin or other mechanism which engages with the first major surface  142  of slidable coupling  140  and fixed buttress  120  in order to retard the axial rotation of slidable coupling  140 . This retardation of axial rotation has the effect of fixing slidable coupling  140  and fixed buttress  120  together such that any axial rotation of slidable coupling  140  necessarily would result in axial rotation of fixed buttress  120  and, correspondingly, shaft  110 . It is also contemplated that rotation lock  150  can take the form of a keyway, i.e., an interlocking tongue-and-groove joint between shaft  110  and slidable coupling  140 . In a preferred embodiment, rotation lock  150  is a pin. In another preferred embodiment, shaft  110  further contains a female dovetail groove which interlocks with a matching male dovetail cutout on slidable coupling  140  to prevent axial rotation. It is also contemplated to reverse the location of the male and female dovetail joints between shaft  110  and slidable coupling  140 . 
         [0013]    First major surface  142  of slidable coupling  140  further contains a selective axial rotation device  160 . Selective axial rotation device  160  can be in the form of a pin, rod, bolt or any other such mechanism known to those skilled in the art. In a preferred embodiment, selective axial rotation device  160  is a pin. Selective axial rotation device  160  is fixedly mounted on the first major surface  142  of slidable coupling  140  and projects outward from first major surface  142  of slidable coupling  140  to engage with selective axial engagement port  162  (shown on  FIG. 2 ) when the shaft lock device is in the “storage” state. Once the shaft lock device is moved to the “in use” state, slidable coupling  140  will move along shaft  110  a sufficient distance such that selective axial rotation device  160  is no longer engaged with selective axial engagement port  162 . Selective axial engagement port  162  can be any hole, depression, etc. which is designed or otherwise able to accept selective axial rotation device  160  and retard the axial rotation of selective axial rotation device  160  when the shaft lock is in the “storage” state. 
         [0014]    Second major surface  144  of slidable coupling  140  contains engagement structure  146 . Engagement structure  146  can be any type of mechanical engagement sufficient to permit the mating of slidable coupling  140  and rotatable coupling  170 . In a preferred embodiment engagement structure  146  is a castle-nut design which has a number of teeth  148  (as shown in  FIG. 5 ). Teeth  148  can be straight, flared or otherwise have an angled cross section in order to provide additional stability when engaged. 
         [0015]    Rotatable coupling  170  has a first major surface  172  and a second major surface  174 . Rotatable coupling  170  is disposed along shaft  110  but is free to rotate axially about shaft  110 . First major surface  172  of rotatable coupling  170  contains engagement structure  176 . Engagement structure  176  is design to be complimentary to engagement structure  146  located on slidable coupling  140  such that once engagement structure  146  and engagement structure  176  are mated, any axial rotation of rotatable coupling  170  is transferred to slidable coupling  140 . In a preferred embodiment, engagement structure  176  is a “castle-nut” type design similar to that employed on slidable coupling  140 . In a preferred embodiment, engagement structure  176  contains teeth  177  (shown in  FIG. 5 ) which serve to engage with the opposing recessed areas between teeth  148  located on engagement structure  146 . In another preferred embodiment, teeth  177  cover a majority of the area of first major surface  172 , thus providing a limited area of “recessed” area between teeth  177 . The limited amount of “recessed” area permits a greater range of motion of rotatable coupling  170  before engagement with slidable coupling  140  during a “test” as would be appreciated by one skilled in the art. In other words, by employing broad teeth  177  on rotatable coupling  170  and narrow teeth  148  on slidable coupling  140 , actuator  200  (shown in  FIG. 2 ) will be able to move rotatable coupling  170  via drive device  179  (shown in  FIG. 2 ) through a limited degree of motion without causing slidable coupling  140  to engage with rotatable coupling  170 . This built-in testing ability is specifically contemplated by the present invention. 
         [0016]    It is also contemplated by the present invention for the top surface  148   1  of teeth  148  and the top surface  177   1  of teeth  177  to be angled (as illustrated in  FIG. 5 .) Top surface  148   1  and top surface  177   1  come into contact during the time the shaft lock is in the “storage” state. Because slidable coupling  140  is under tension from stored energy device  130 , slidable coupling  140  can have a tendency to rotate under vibration when in the “storage” state. Thus, by providing an angle for top surface  148 ′ and the corresponding top surface  177   1  along with broad teeth  177  on rotatable coupling  170 , undesired rotation of the shaft lock device  10  under vibration when in “storage” can be achieved more successfully than if top surfaces  148   1  and  177   1  were flat. In a preferred embodiment, the direction of the angle of top surfaces  148   1  and  177   1  is selected such that the tension exerted by stored energy device  130  serves to force rotatable coupling  170  to rotate in the opposite direction as is necessary for engagement of the shaft lock device  10  into the ‘in use’ state. 
         [0017]    Rotatable coupling  170  further contains an attachment port  178 . Attachment port  178  can be a pin, bolt, hole, bracket or any other such mechanism which permits a drive device  179  to be engagebly connected to rotatable coupling  170 . Drive device  179  can be a screw, pin or any other drive mechanism know to those in the art which can be attached to an actuator motor, piston, etc. and transfer energy or force from the actuator itself to attachment port  178  and thus apply the energy or force to rotatable coupling  170  causing it to rotate about shaft  110 . In the embodiment illustrated in  FIG. 2 , drive device  179  is a screw-threaded shaft. In a preferred embodiment, attachment coupling  180  is provided to facilitate the attachment of drive device  179  with actuator attachment port  178 . A shown in  FIG. 1 , attachment coupling  180  is a threaded bolt machined to accept the insertion of drive device  179 . Attachment coupling  180  can also be selected from any known configuration of mechanical connectors which would service to permit the engagement of drive device  179  with attachment port  178 . Drive device  179  can be any structure suitable to transfer movement from an actuator to rotatable coupling  170 . Linear actuators are contemplated by some embodiments of the present invention, however gear drives or any other known actuator can be employed. 
         [0018]    Shaft lock device  10  further comprises a mounting device  190  which is fixedly attached to the support structure of the missile, rocket etc. Mounting device  190  is designed to permit second major surface  174  of rotatable coupling  170  to seat and remain rotatably in place. Axial pin  210  is fixedly mounted to the inside of rotatable coupling  170  along with potentiometer  212 . Potentiometer  212  is used to gather and report rotational data concerning the position of rotatable coupling  170  while in storage, testing or flight. As illustrated in  FIG. 1 , potentiometer  212  is of a cartridge pot design as known to one skilled in the art, however all other types of position sensors which serve to provide rotational information as known to those in the art can be employed. 
         [0019]      FIG. 2  illustrates an embodiment of the present invention in the “storage” state. That is, slidable coupling  140  has not yet engaged with rotatable coupling  170 . As shown in  FIG. 2 , during the “storage” state, engagement structure  146  and engagement structure  176  have not been mated. As such, teeth  148  and teeth  177  are resting against each other and slidable coupling  140  is inhibited from moving axially toward rotatable coupling  170 . Additionally, axial rotation device  160  is engaged with selective axial engagement port  162  which prevents the axial rotation of slidable coupling  140  and, by connection to shaft  110 , the axial rotation of fin  100 . In  FIG. 2 , drive device  179  is a screw-threaded shaft. Thus, the selective shaft lock device of the present invention provides for a “storage” state in which fin  100  is locked in position. 
         [0020]      FIG. 3  illustrates the “in use” state of an embodiment of the present invention. According to the present invention, when it is desired to move from the “storage” state to the “in use” state, a force is applied to drive device  179 . In the illustration of  FIG. 3 , an actuator (not shown) would rotate the screw-threaded shaft which comprises drive device  179 . Such an application of force has the effect of axially rotating rotatable coupling  170  and moving engagement structure  176  into a position relative to engagement structure  146  such that the force applied by stored energy device  130  to slidable coupling  140  causes slidable coupling  140  to engage with rotatable coupling  170 . As will be appreciated by one skilled in the art, the size and dimensions of engagement structure  146  and engagement structure  176  is preferably such that the minimum distance necessary for slidable coupling  140  to engage rotatable coupling  170  is greater than the distance selective axial rotation device  160  projects into selective axial engagement port  162 . Thus, once slidable coupling  140  engages with rotatable coupling  170 , rotatable coupling  170  is now free to rotate about shaft  110  and any force applied to rotatable coupling  170  via drive device  179  will act upon slidable coupling  140 , and necessarily fin  100  given that both slidable coupling  140  and fin  100  are fixedly attached to shaft  110  (as shown in  FIG. 1 ). 
         [0021]    As would be appreciated by one skilled in the art, although the embodiments described herein illustrate a shaft lock device  10  in which slidable coupling  140  slides inward to engage with rotatable coupling  170 , it is contemplated by the present invention to reverse the orientation of slidable coupling  140  and rotatable coupling  170 . Configurations having slidable coupling  140  slide outward (relative to the missile, rocket, etc.) to engage with rotatable coupling  170  are specifically within the scope of the present invention. Further, embodiments mounting fixed energy device  130  against the internal structure of the missile, rocket, etc. as opposed to fixed buttress  120  and constructing the remainder of the shaft lock device of the present invention as taught herein are within the scope of this invention. 
         [0022]    Referring to  FIG. 4 , it is further contemplated by the present invention to provide an access point  220  at a location in the vicinity of fin  100 . Access point  220  can be either an open hole or a hole with a corresponding cover to maintain the aerodynamic profile of the missile, rocket, etc. In the embodiment illustrated in  FIG. 4 , access point  220  is a hole. Access point  220  permits the insertion of a retraction device  230  such as a hook, pliers, etc. In a preferred embodiment, retraction device  230  is an L-shaped tool. Retraction device  230  can be inserted into access point  220  and then engage with the second major surface  144  of slidable coupling  140 . Once engaged, retraction device  230  can be used to disengage slidable coupling  140  from rotatable coupling  170 . Once slidable coupling has been retracted a sufficient distance, actuator  200  can be operated to rotate rotatable coupling  170  into a position such that engagement structure  146  and engagement structure  176  are orientated in a “storage” fashion and unable to engage with each other (as illustrated in  FIG. 2 ). Retraction device  230  can then be removed via access point  220  and the shaft lock device has been returned to the “storage” position. 
         [0023]    It is understood that the above description is intended to be illustrative and not restrictive. Although various characteristics and advantages of certain embodiments of the present invention have been highlighted herein, many other embodiments will be apparent to those skilled in the art without deviating from the scope and spirit of the invention disclosed. The scope of the invention should therefore be determined with reference to the claims contained herewith as well as the full scope of equivalents to which said claims are entitled. 
         [0024]    Now that the invention has been described,