Abstract:
A device is provided for holding and releasing a missile within a canister. The device includes a housing attached to the canister, a latch mechanism extending from the housing into the canister, a tension applier disposed in the housing to restrain the missile in the canister, a release mechanism disposed on the housing, an interface mechanism and a compression applier. The tension applier forces the latch mechanism against the housing to withdraw from the missile. The interface mechanism initially couples the release mechanism and the tension applier. The compression applier anchors to the interface mechanism and forces the latch mechanism against the housing to engage the missile and counteract said tension applier. On command, the release mechanism disengages from the housing to release the compression applier from the interface mechanism. This action enables the tension applier to withdraw the latch mechanism from the missile.

Description:
STATEMENT OF GOVERNMENT INTEREST 
   The invention described was made in the performance of official duties by one or more employees of the Department of the Navy, and thus, the invention herein may be manufactured, used or licensed by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 

   BACKGROUND 
   The invention relates generally to a hold-and-release mechanism. In particular, the mechanism maintains a thrust-generating missile within a deployment canister until release by command. 
   Select munitions can be launched from canister platforms, such as torpedoes and ship-launched missiles. Vertically launched missiles may be held in place by releasable clamps or shearable pins. A missile deployed within a launch tube and equipped with a solid rocket motor booster may be ejected from its canister by gas (e.g., steam) subsequently propelled by its booster. For launch from a submarine, the motor firing may be initiated after rising above the water&#39;s surface. 
   SUMMARY 
   Conventional mechanisms for restraining a canisterized missile yield disadvantages addressed by various exemplary embodiments of the present invention. These various exemplary embodiments provide a device for holding and releasing a missile within a canister. In particular, the device includes a housing attached to the canister, a latch mechanism extending from the housing into the canister, a tension applier disposed in the housing to restrain the missile in the canister, a release mechanism disposed on the housing, an interface mechanism and a compression applier. 
   The tension applier forces the latch mechanism against the housing to withdraw from the missile. The interface mechanism initially couples the release mechanism and the tension applier. The compression applier anchors to the interface mechanism and forces the latch mechanism against the housing to engage the missile and counteract said tension applier. On command, the release mechanism disengages from the housing to release the compression applier from the interface mechanism. This action enables the tension applier to withdraw the latch mechanism from the missile. 
   In various exemplary embodiments, the release mechanism is an electrically activated threaded explosive bolt. In alternate embodiments, the interface mechanism is a plate pivotably connected to the housing by a hinge. In various exemplary embodiments, the compression applier is an adjustable threaded compression bolt. Alternate embodiments provide for the housing to include a base that attaches to the canister, a chamber that contains the tension applier and a stub that attaches to the release mechanism. Various preferred embodiments provide for the release mechanism to include a sealing mechanism to inhibit leakage. The tension applier may be represented by a helical spring, and the latch mechanism may be represented by a push-rod. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and various other features and aspects of various exemplary embodiments will be readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, in which like or similar numbers are used throughout, and in which: 
       FIG. 1  is shows an exploded perspective view of components for a hold release mechanism; 
       FIG. 2  is an assembly perspective view of the hold release mechanism; 
       FIG. 3  is a perspective view of a push-rod assembly; 
       FIG. 4  is a see-through perspective view of the hold release mechanism; 
       FIG. 5  is an elevation view of the hold release mechanism in operation; 
       FIG. 6  is an elevation view of time-elapsed travel positions for components of the hold release mechanism; 
       FIG. 7  is a perspective side view of the hold release mechanism as installed on a canister; 
       FIG. 8  is a perspective aft view of the canister with four hold release mechanisms installed; 
       FIG. 9  is a perspective side view of the canister prior to launch initiation; 
       FIG. 10  is a perspective side view of the release mechanism subsequent to launch initiation; and 
       FIG. 11  is an elevation diagram of time-elapsed missile positions in the canister. 
   

   DETAILED DESCRIPTION 
   In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized, and logical, mechanical, and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. 
   One submarine-based missile launch platform under consideration for operational depths is the Water Piercing Missile Launcher (WPML), which uses the rocket motor&#39;s exhaust to pierce the water. Upon production of an exhaust gas column that reaches the surface, the missile can be released to traverse the surface and continue towards its target. Various exemplary embodiments provide a hold and release mechanism (HRM) to restrain the missile during initial motor firing until conditions merit the missile to be released. 
     FIG. 1  shows an exploded perspective view of components  100  for the HRM. A base plate  110  may be welded or bolted to a missile canister (to be subsequently described in more detail). Along the exposed surface of the plate  110  opposite the canister are disposed a pair of hollow cylinders: a larger-diameter barrel  120  and a smaller-diameter explosive tube  125 . A helical release spring  130  may be disposed into the barrel  120  along their common longitudinal axes. A push-rod or pin  140  may be inserted within the release spring  130  along the common axis as installed. The barrel  120  and explosive tube  125  may be welded to the base plate  110  and together form the HRM housing. 
   A hinge plate  150  may be disposed over the hollow cylinders  120 ,  125 , with a corresponding pair of through-holes aligned thereto. The hinge plate  150  may be characterized as having a substantially circular platform (having a center through-hole) and flanked by (nonsymmetrical) wing tabs (one of which includes a distal through-hole). An end plate or flat washer  155  having a center through-hole may be disposed between the hinge plate  150  and the open end of the barrel  120 . A compression bolt  160  may be inserted through the center through-holes of the hinge plate  150  and the end plate  155 . A threaded bolt  165  disposed between the plates  150 ,  155  may secure the bolt  160  in position to restrain the pin  140 . The compression bolt  160  may have a predetermined length depending on design requirements. 
   An explosive bolt  170  may be disposed through the distal through-hole of the hinge plate  150  for insertion into the explosive tube  125 . The explosive bolt  170  includes an energetic primer triggered to explode in response to electric current through circuit wires  175  that extend from the bolt&#39;s top. The distal wire  175   a  represents the hot wire typically colored red. The proximal wire  175   b  represents the neutral wire typically colored black. In the exemplary embodiments shown herein, the bolts  160 ,  170  are threaded for adjustably screwing in place. 
   A bracket  180  may be disposed adjacent to the open end of the barrel  120  opposite from the explosive tube  125 . The bracket  180  may include a pair of axial through-holes yielding an axis substantially parallel to the base plate  110  and substantially perpendicular to a plane formed by the longitudinal axes of the cylinders  120 ,  125 . A clevis pin  185  passes through the bracket&#39;s through-holes and a hinge sleeve  190  disposed on the hinge plate  150 . The clevis pin  185  may be secured by a cotter pin. The barrel  120  and explosive tube  125  may be welded to the base plate  110  and together with the bracket  180  form the HRM housing. 
     FIG. 2  shows a perspective view of the HRM as an assembly  200 . The push-rod  140  extends opposite the exposed surface of the base plate  110  (and into the canister). The barrel  120  and explosive tube  125  extend from the base plate  110 . The hinge plate  150  with the bolts  160 ,  170  extending there-through is disposed over the open end of the cylinders  120 ,  125 , and the bracket  180  enables the hinge plate  150  to swing open upon commanded rupture of the explosive bolt  170 . 
     FIG. 3  shows a perspective view of a push-rod assembly  300  for sealing the barrel  120 . The push-rod  140  may be secured to a stem  310  for connection to the base plate  110  and enveloped proximate to the stem  310  by a coil seal spring  320  terminated at each end by a pair of rubber tap washers  330  and  340 . The proximal washer  330  may be disposed adjacent to the stem  310 , while an o-ring  350  may form an annular seal around the push-rod  140 . Upon assembly, the stem  310 , spring  320 , washers  330 ,  340  and o-ring  350  may be contained within the barrel  120 , with the push-rod  140  protruding beyond the o-ring  350 . This design inhibits leaking of liquid into the barrel  120 , thereby enabling a water tight seal between the HRM and the WPML. 
     FIG. 4  shows a partially see-through perspective view of the HRM assembly  400 , featuring internal components from  FIGS. 1 and 3  as installed and assembled in  FIG. 2 . This configuration illustrates the compression bolt  160  prior to being fully screwed in the hinge plate  150  to squeeze the release spring  130 , with the seal spring  320  and distal washer  340  nestled within and around the push-rod  140 . The explosive bolt  170  visibly shows the scored region for separation, with its distal portion (inserted into the tube  125  and opposite the wires  175 ) containing the primer for command release via electric current. 
   The HRM represents as a cost effective mechanism to restrain a missile for a predetermined time before enabling its exit from the launcher. The mechanism assembly  200  engages the push-rod  140  through the canister (along its cylindrical wall) and into the missile. Four of these mechanisms may be disposed in a cruciform pattern, for example, to ensure force balance along the missile&#39;s longitudinal centerline. Upon firing the missile&#39;s rocket motor, the push-rod  140  restrains the missile from flying out until a column of exhaust gas punches a hole through the water. Once this column has formed, all push-rods  140  are pulled for each of the assemblies  200  pulled, thereby enabling the missile to fly through the column unabated. 
   Scale tests were conducted in which the push-rods  140  were pulled with explosive pin pullers. Such a puller includes a piston disposed over an explosive charge and attached to a heavy pin. Upon initiating the charge, the rapidly expanding gasses move the piston, thereby pulling the push-rod  140  to release the missile. Typically, these must explosively tailored to the application, are single-use only and can be quite expensive. The HRM may serve as a pin puller for missile launch applications with advantages of design flexibility and repeatable operations with substantially the same equipment, except for the explosive bolt  170  that is consumed at launch. 
   Assembly instructions for the HRM based on the views in  FIGS. 1-3  are listed as follows: 
   (1) Attach the hinge plate  150  to the barrel  120  of the HRM housing by inserting the clevis pin  185  secured with a cotter pin. The hinge plate  150  preferably rotates freely about the clevis pin  185 , disposed at rest preferably flush with the barrel&#39;s open end.
 
(2) Install the release spring  130  in the barrel  120 .
 
(3) Assemble the push-rod  140  within its assembly  300 . This includes the operations:
 
   (a) Thread the push-rod  140  into stem  310  and secure with a nut. 
   (b) Install the proximal washer  330  under the stem  310 . 
   (c) Install the seal spring  320 . 
   (d) Install the distal washer  340  over the seal spring  320 . 
   (e) Install the o-ring  350  under the distal washer  340 . 
   (4) Install push-rod assembly  300  into the barrel  120 , such that the push-rod  140  protrudes beyond the base plate  110 . 
   (5) Install a grade-8 bolt in place of the explosive blot  170  and tighten, but not excessively. A torque of 50 inch-pounds may be used as an example reference. 
   (6) Install 1¼ inch grade-8 compression bolt  160  with the end plate  165 . 
   (7) Tighten the bolt  160  until being in contact with hinge plate  150  then torque to 150 inch-pounds. 
   (8) Measure length of the push-rod  140  extending from the base plate  110 . Slight adjustments may be made by threading the push-rod  140  farther into stem  310 . 
   After the hinge plate  150  contacts the barrel  120  and the explosive bolt  170  is disposed in place and tightened, the compression bolt  160  can be tightened down and torqued. When tightened, the compression bolt  160  presses against the push-rod  140  threaded into the stem  310  to push against and restrain the missile in the canister. The end plate  155  (connected to the hinge plate  150 ) uniformly presses against the distal end of the release spring  130  to compress it. Upon initiating the explosive bolt  170 , the hinge plate  150  rotates about the clevis pin  185  releasing the push-rod  140  to be pushed out by the force of the release spring  130 . 
     FIG. 5  shows an example of the HRM operation  500  during initiation of the explosive bolt  170 . The position sequences are shown in four (4) stages: loaded  510 , activated  520 , travel  530  and release  540 . In the loaded position  510 , the explosive bolt  170  is fastened in place and the central bolt  160  is fully engaged, thereby compressing the release spring  130 . 
   Upon initiation of the explosive bolt  170  in the activated position  520 , the tensile force by the release spring  130  against the compression bolt  160  causes the hinge plate  150  to rotate about the clevis pin  185  in an involute curve trajectory, which continues into the travel position  530 . The compression bolt  160  can be screwed a substantial distance into the barrel  120  to fully deflect the release spring  130 , and nonetheless withdraw in the release position  540  without contacting the interior side of the barrel  120  upon ejection. As the compression bolt  160  rotates in the release position  540 , the release spring  130  extends within the barrel  120  towards its open end, thereby withdrawing the push-rod  140  (at least partially) from the canister to release the missile. 
     FIG. 6  shows an elevation view of travel trajectory positions  600  of select components for a 0.50 inch diameter compression bolt  160 . The hinge plate  150  follows an offset rotation path  610  around the clevis pin  185 . The plate&#39;s inner surface (initially facing the open end of the barrel  120  in the loaded position  510 ) is depicted along the rotation path  610  as a series of swinging path plate positions  620 . The hinge plate  150  is pushed by the release spring  130  in response to retreat by the compression bolt  160  along a swinging bolt path  630  within an inner cylindrical diameter  640  of the barrel  120 . 
   Dimensions as shown in  FIG. 6  indicate an exemplary embodiment for recently conducted tests. In this example, the barrel  120  has an internal cylindrical diameter of 1.60 inches, and the compression bolt  160  extends 1.50 inches into the barrel  120  (which may be 3.50 inches in length). 
     FIG. 7  shows an installed configuration  700  in perspective view from the side with the base plate  110  of the HRM assembly  200  disposed on a canister. The compression bolt  160  is shown prior to being screwed into the barrel  120 . The wires  175  (attached to the explosive bolt  170  in the tube  125 ) are wrapped within an insulation cable  710 . The  FIG. 8  shows an installed configuration  800  in perspective from the rear with each HRM assembly  200  securely attached to an outer annulus (attach ring)  810  of the canister that contains a simulated missile  820  within an inner annulus  830 . A cruciform set of plates  840  secures the inner annulus  830  to the outer annulus  810 . The push-rods  140  from the HRM assemblies  200  pass through the plates  840  to restrain the (simulated) missile  820 . 
     FIG. 9  shows another perspective view  900  of the canister&#39;s outer annulus  810  and the attached HRM assemblies  200  from the side (prior to the compression bolt  160  being tightened).  FIG. 10  shows a perspective view  1000  of the HRM assembly  200  after initiation, in which the compression plate  160  has been hinged away from the barrel&#39;s opening after the explosive bolt&#39;s discharge. 
     FIG. 11  shows an elevation view  1100  of launching stages for the WPML into the atmosphere  1110  from deployment under water  1120  between the water&#39;s surface  1125  and the submarine-deployed canister  1130 . The missile  1135  can be ejected by firing its motor to produce exhaust gas  1140  thereby producing a gas column  1145  thereby piercing the water  1120  to its surface  1125 . The stages include pre-launch  1150 , motor firing  1160 , column production  1170 , missile release  1180  and missile fly-out  1190  beyond the surface  1125 . The HRM assemblies  200  restrain the missile  1135  until the gas column  1145  reaches the surface  1125  (and the motor&#39;s thrust is sufficient to propel the missile  1135 ) out of the canister  1130 . 
   The HRM was tested successfully in design mode at least sixteen times. The final test (to date) in September 2007 incorporating four (4) HRM units produced a successful missile fly-out and proof-of-concept for the WPML. Further tests are expected as the WPML program evolves. 
   In general, the time from initiation of the rocket motor to the time when the HRM is activated, varies with application and rocket motor type. For the September 2007 successful WPML missile fly-out test, experimental data indicated that the missile  1135  should be held within the canister  1130  for approximately one second to form a stable column  1145 . At this time, the explosive bolt  170  was initiated through a time-delay switch, enabling the push-rod  140  to release the missile  1135 . 
   The HRM assembly  200  is flexible in design, such that stronger or weaker springs  130 ,  320  may be used. The HRM assembly  200  can be made dimensionally smaller or larger depending on the application. For example, an upcoming WPML program may employ a Tomahawk rocket motor, which has substantially greater thrust than the Jato rocket motor used in the September 2007 test. Artisans of ordinary skill will recognize that substituting springs of different strength and/or scaling particular dimensions may augment the HRM design for specific applications without departing from the inventive concept. 
   In principle, the HRM assembly  200  can be described as including a housing, a pivotable interface, a latching mechanism, a tension applier, an adjustable compression applier and a release mechanism. The housing may include the base plate  110  with the barrel  120  (e.g., chamber for the latching mechanism and tension applier) and the tube  125  (e.g., stub for the release mechanism). 
   In the configuration shown, the barrel  120  and tube  125  may be connected (e.g., by welding) on the base plate&#39;s outer surface. Similarly, the plate&#39;s lower surface may connected to the canister  1130  (by welding), and the bracket  180  may be attached near the open end of the barrel  120 . The pivotable (i.e., swingable on a pivot) interface may be represented by the hinge plate  150  coupled with the end plate  155  and the nut  165 . The interface may be hinged, for example, on the sleeve  190  to the clevis pin  185 . This interface couples the tube  125  with the barrel  120  to be secured and released concurrently. 
   The latching mechanism (or latch) may be represented by the push-rod  140  that restrains the missile  1135  in the canister  1130 . The adjustable compression applier may be represented by the compression bolt  160  to dispose the latch against the missile  1135 . The release mechanism may be represented by the explosive bolt  170  that initially secures the interface to the housing for its subsequent withdrawal on command. The tension applier may be presented by the release spring  130  to drive the latch away from the missile  1135  for its launch from the canister  1130  upon activation of the release mechanism. 
   The HRM includes various advantages, such as being inexpensive as compared with the alternate explosive pin pullers. The HRM can be manufactured from off-the-shelf materials, and explosive bolts  170  are readily available and easily manufactured items. The HRM is reusable, with the exception of the explosive bolts. The HRM can be scaled in size and strength to function in different configurations and to overcome different load requirements. 
   While certain features of the embodiments of the invention have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments.