Patent Publication Number: US-2021179281-A1

Title: Releasable restraint for evacuation assemblies

Description:
FIELD 
     The present disclosure relates to releasable restraints, and more specifically to releasable restraint devices for evacuation assemblies. 
     BACKGROUND 
     Evacuation assemblies may include an inflatable slide that helps passengers disembark from an aircraft in the event of an emergency or other evacuation event. The slides may deploy from a door sill or a side of the aircraft fuselage. Deployment and/or unfolding of the slide is controlled by restraints placed throughout the length of the slide. The restraints typically include a shear pin, which shears (or breaks) in response to internal slide pressure. In this regard, the shear pin and/or the restraints are generally single use. 
     SUMMARY 
     A releasable restraint is disclosed herein. In accordance with various embodiments, the releasable restraint may comprise a base and a socket coupled to the base. The socket may include a head and a shaft extending from the head. A sleeve may be configured to translate relative to the shaft of the socket. A plurality of balls may be located in the shaft of the socket. A plug may be configured to be received by a plug groove defined by the socket. 
     In various embodiments, the plug may define a ball groove. In various embodiments, the sleeve may include an interference surface radially outward of the plurality of balls. In various embodiments, the interference surface may be non-parallel to a center axis of the sleeve. 
     In various embodiments, the interference surface may contact the plurality of balls. In various embodiments, a spring may be configured to bias the sleeve toward the head of the socket. In various embodiments, the spring may be located in a spring cavity defined by the base, the socket, and the sleeve. 
     An evacuation slide is also disclosed herein. In accordance with various embodiments the evacuation slide may comprise a first strap coupled to a first portion of the evacuation slide, a second strap coupled to a second portion of the evacuation slide, and a first releasable restraint coupled between the first strap and the second strap. The first releasable restraint may comprise a first base coupled to the second strap and a first socket coupled to the first base. The first socket may include a first head and a first shaft extending from the first head. The first releasable restraint may further comprise a first sleeve configured to translate relative to the first shaft, a plurality of first balls located in the first shaft, and a first plug coupled to the first strap and configured to be received by a first plug groove defined by the first socket. 
     In various embodiments, the first releasable restraint may further comprise a first spring configured to bias the first sleeve toward the first head of the first socket. In various embodiments, the first sleeve may include a first interference surface radially outward of the plurality of first balls. The first interference surface may be oriented at a first angle relative to a first center axis of the first sleeve. 
     In various embodiments, a third strap may be coupled to a third portion of the evacuation slide. A fourth strap may be coupled to a fourth portion of the evacuation slide. A second releasable restraint may be coupled between the third strap and the fourth strap. The second releasable restraint may comprise a second base coupled to the fourth strap and a second socket coupled to the second base. The second socket may include a second head and a second shaft extending from the second head. The second releasable restraint may further comprise a second sleeve configured to translate relative to the second shaft, a plurality of second balls located in the second shaft, and a second plug coupled to the third strap and configured to be received by a second plug groove defined by the second socket. 
     In various embodiments, the first strap may be coupled closer to a head end of the evacuation slide as compared to the third strap. In various embodiments, the second sleeve may include a second interference surface radially outward of the plurality of second balls. The second interference surface may be oriented at a second angle relative to a second center axis of the second sleeve. The second angle may be different from the first angle. 
     In various embodiments, the second releasable restraint may further comprise a second spring configured to bias the second sleeve toward the second head of the second socket. A first spring constant of the first spring may be different from a second spring constant of the second spring. 
     In various embodiments, a radially outward surface of the first plug may define a first ball groove. In various embodiments, a diameter of the first plug, as measured at the radially outward surface, may decrease proximate an axial end of the first plug. 
     A deployment assembly is also disclosed herein. In accordance with various embodiments, the deployment assembly may comprise a releasable restraint including a base and a socket coupled to the base. The socket may include a head and a shaft extending from the head. A sleeve may be configured to translate relative to the shaft. A plurality of balls may be located in the shaft. A spring may be configured to bias the sleeve toward the head of the socket. A plug may be configured to be received by a plug groove defined by the socket. 
     In various embodiments, a first shackle may be coupled to the base. A second shackle may be coupled to the plug. In various embodiments, the sleeve may include an interference surface radially outward of the plurality of balls. The interference surface may be non-parallel to a center axis of the sleeve. In various embodiments, the plug may define a ball groove configured to receive the plurality of balls. 
     The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated herein otherwise. These features and elements as well as the operation of the disclosed embodiments will become more apparent in light of the following description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrate an evacuation slide in a deployed position, in accordance with various embodiments; 
         FIGS. 2A and 2B  illustrate a releasable restraint retaining an evacuation slide in a folded, or “stowed,” position, in accordance with various embodiments; 
         FIGS. 3A and 3B  illustrate a perspective view and a cross-section view, respectively, of a releasable restraint in a secured position, in accordance with various embodiments; 
         FIG. 4  illustrates a cross-section view of a socket of a releasable restraint, in accordance with various embodiments; 
         FIG. 5  illustrates a cross-section view of a plug of a releasable restraint, in accordance with various embodiments; 
         FIG. 6  illustrates a cross-section view of a releasable restraint during evacuation slide deployment, in accordance with various embodiments; and 
         FIG. 7  illustrates a cross-section view of a releasable restraint during separation of the plug, in accordance with various embodiments; 
         FIG. 8  illustrates a cross-section view of releasable restraint in a separated position, in accordance with various embodiments; 
         FIG. 9  illustrates a cross-section view of a releasable restraint during insertion of the plug of the releasable restraint, in accordance with various embodiments; and 
         FIGS. 10A, 10B, and 10C  illustrate staged deployment of an evacuation slide, in accordance with various embodiments. 
     
    
    
     The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, may best be obtained by referring to the detailed description and claims when considered in connection with the drawing figures, wherein like numerals denote like elements. 
     DETAILED DESCRIPTION 
     The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the exemplary embodiments of the disclosures, it should be understood that other embodiments may be realized and that logical changes and adaptations in design and construction may be made in accordance with this disclosure and the teachings herein. Thus, the detailed description herein is presented for purposes of illustration only and not limitation. The steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented 
     Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact. Surface cross hatching lines may be used throughout the figures to denote different parts but not necessarily to denote the same or different materials. 
     Throughout the present disclosure, like reference numbers denote like elements. Accordingly, elements with like element numbering may be shown in the figures, but may not be necessarily be repeated herein for the sake of clarity. 
     Releasable restraints, as disclosed herein, may aid in controlling inflation and deployment of evacuation slides. In accordance with various embodiments, the releasable restraints may be configured to separate or de-couple in response to an increased internal slide pressure. After deployment, the separated pieces of the releasable restraint may be re-attached to one another such that the same releasable restraint can be used multiple times. In this regard, the releasable restraints, as described herein, are reusable. Reusable releasable restraints may provide cost saving, particularly, with regard to slide testing and certification, wherein multiple deployments of an evacuation slide are performed. 
     With reference to  FIG. 1 , an evacuation slide  100  is illustrated, in accordance with various embodiments. Evacuation slide  100  may deploy from an aircraft, such as from, for example, an aircraft fuselage or aircraft wing. Evacuation slide  100  may comprise a head end  102  and a toe end  104  opposite head end  102 . Head end  102  may be coupled to an aircraft. Evacuation slide  100  may comprise a sliding surface  106  and an underside surface  108  that is opposite sliding surface  106 . Toe end  104  of evacuation slide  100  may be configured to contact an exit surface in response to evacuation slide  100  being deployed. Evacuation slide  100  may be an inflatable slide.  FIG. 1  illustrates evacuation slide  100  in an inflated or “deployed” position. Evacuation slide  100  may comprise a dual lane slide. However, evacuation slide  100  may comprise any number of lanes. 
     With reference to  FIGS. 2A and 2B , evacuation slide  100  is illustrated in a stowed position. When evacuation slide  100  is in the stowed position, evacuation slide  100  may include one or more folds, such as first fold  110  and second fold  112 . Evacuation slide  100  may include a deployment assembly  114 . Deployment assembly  114  may aid in a staged deployment of evacuation slide  100 . Deployment assembly  114  includes one or more releasable restraint(s)  120  ( FIG. 2B ). Releasable restraint  120  may aid in maintaining first fold  110  and/or second fold  112  and/or in the staged deployment of evacuation slide  100 . In accordance with various embodiments, evacuation slide  100  may unfold (i.e., deploy) in response to separation of releasable restraint  120 . 
     In various embodiments, releasable restraint  120  may be configured to separate in response to an internal pressure of evacuation slide  100  exceeding a threshold pressure. For example, a gas cylinder may supply a flow of pressurized fluid to evacuation slide  100  in response to evacuation slide  100  being deployed. Evacuation slide  100  may begin to inflate and an internal pressure of evacuation slide  100  may increase. Releasable restraint  120  may maintain evacuation slide  100  in the folded position until the internal pressure has increased to greater than a predetermined threshold pressure. Releasable restraint  120  may separate in response to the internal pressure of evacuation slide  100  being greater than the predetermined threshold pressure. Evacuation slide  100  may unfold in response to releasable restraint  120  separating. 
     In various embodiments, deployment assembly  114  may include a first shackle  122  and a second shackle  124 . First shackle  122  may be coupled between releasable restraint  120  and a first strap  126 . Second shackle  124  may be coupled between releasable restraint  120  and a second strap  128 . First and second straps  126 ,  128  may comprise rope, tape, ribbon, webbing, or any other desired material. An end  132  of first strap  126  may form a loop through which first shackle  122  is located. An end  134  of second strap  128  may form a loop through which second shackle  124  is located. A cover  136  may surround releasable restraint  120 . Cover  136  may comprise a fabric. For example, cover  136  may comprise nylon, ballistic nylon, polypropylene, polyester, cotton, or other desired material. 
     First and second straps  126 ,  128  may each be coupled to evacuation slide  100 . First strap  126  may be coupled to a first portion  138  of evacuation slide  100 . Second strap  128  may be coupled to a second portion  140  of evacuation slide  100 . In various embodiments, second portion  140  is closer to toe end  104  (with momentary reference to  FIG. 1 ) of evacuation slide  100  as compared to first portion  138 . In various embodiments, first portion  138  may be located on sliding surface  106  (with momentary reference to  FIG. 1 ) and second portion  140  may be located on underside surface  108  (with momentary reference to  FIG. 1 ). During inflation of evacuation slide  100 , the increasing internal pressure of evacuation slide  100  tends to cause first and second straps  126 ,  128  to translate away from one another, thereby causing a force  142  in opposing directions to be applied to releasable restraint  120 . As described in further detail below, releasable restraint  120  is configured to decouple or separate in response to the force  142  applied by first and second straps  126 ,  128  exceeding a predetermine threshold force (i.e., in response to the internal pressure of evacuation slide  100  exceeding a predetermined threshold pressure). 
     With reference to  FIGS. 3A and 3B , a releasable restraint  120  is illustrated.  FIG. 3A  illustrates a perspective view of releasable restraint  120 , and  FIG. 3B  illustrates a cross-section view of releasable restraint taken along the line  3 B- 3 B in  FIG. 3A . In accordance with various embodiments, releasable restraint  120  includes a base  152 , a socket  154  coupled to the base  152 , and a sleeve  156  located around the base  152  and the socket  154 . Socket  154  may be coupled to base  152  via, for example, threaded engagement, a press fitting or friction coupling, or any other suitable attachment means. In accordance with various embodiments, releasable restraint  120  further includes a plug  158  releasably coupled to socket  154 . Releasable restraint  120  further includes a spring  160  located in a spring cavity  162  defined by base  152 , socket  154 , and sleeve  156 . Spring  160  applies a biasing force against sleeve  156 . Spring  160  is configured to bias sleeve  156  away from base  152 . Base  152  includes a spring surface  164 . Sleeve  156  includes a spring surface  166 . Spring  160  is located between spring surface  164  and spring surface  166 , and may be in contact with spring surface  164  and/or spring surface  166 . Spring  160  is configured to force spring surface  166  of sleeve  156  away from spring surface  164  of base  152  (i.e., in the direction of arrow  168 ). 
     In various embodiments, base  152  may define an opening  170 . Plug  158  may define an opening  172 . With momentary combined reference to  FIGS. 3A and 2B , opening  170  may be configured to receive second shackle  124 . Opening  172  may be configured to receive first shackle  122 . Second shackle  124  may be located through opening  170 . First shackle  122  may be located through opening  172 . In this regard, first strap  126  may be coupled to plug  158  via first shackle  122 , and second strap  128  may be coupled to base  152  via second shackle  124 . 
     Referring to  FIG. 3B , in accordance with various embodiments, releasable restraint  120  further includes a plurality of spherically-shaped balls, or beads,  180 . Each ball  180  may be located in a ball opening  182  defined by socket  154 . 
     With reference to  FIG. 4 , a cross-section view of socket  154  is illustrated. In accordance with various embodiments, the walls  184  defining ball opening  182  may be slanted, such that a diameter of ball opening  182  increases in the radially outward direction. Ball opening  182  may have a generally conical or frustoconical shape. Socket  154  may include a head  186  and a shaft  188  extending from head  186 . Ball openings  182  may be formed in shaft  188 . Socket  154  defines a base channel  190 . Shaft  188  may define base channel  190 . Base channel  190  may be formed in a first axial end  192  of socket  154 . Base channel  190  is configured to receive base  152 , with momentary reference to  FIG. 3B . Base channel  190  has a diameter D 1 . Diameter D 1  may be selected such that base  152  may be press fit in socket  154 , thereby forming a friction coupling between base  152  and socket  154 . In various embodiments, the radially inward surface  194  that defines base channel  190  may be threaded and configured to engage a threaded surface of base  152 . Socket  154  further defines a plug channel  196 . Plug channel  196  may be defined by head  186  and the portion of shaft  188  proximate head  186 . Plug channel  196  may be formed in a second axial end  198  of socket  154 . Plug channel  196  is configured to receive plug  158 , with momentary reference to  FIG. 3B . In various embodiments, a diameter D 2  of plug channel  196  may be less than diameter D 1  of base channel  190 . In various embodiments, diameter D 2  decreases in an area  200  of plug channel  196 . Area  200  of plug channel  196  may be distal head  186  and second axial end  198  (i.e., closer to base channel  190  as compared to second axial end  198 ). Area  200  may be configured to receive a slanted portion  201  (with momentary reference to  FIG. 5 ) of plug  158 . A radially inward surface  202  of socket  154  defines plug channel  196 . In accordance with various embodiments, a diameter D 3  of ball opening  182 , as measured at radially inward surface  202 , is less than a diameter D 4  of ball opening  182 , as measured at radially outward surface  204  of shaft  188 . 
     Returning to  FIG. 3B , when releasable restraint  120  is in the attached or secured position, (i.e., when plug is coupled to socket  154  and base  152 ), balls  180  may be located in a ball groove  210  defined by plug  158 . With reference to  FIG. 5 , a cross-section view of plug  158  is illustrated. In accordance with various embodiments, ball groove  210  may be formed in a radially outward surface  212  of plug  158 . Ball groove  210  extends radially inward from radially outward surface  212 . In various embodiments, the radially extending walls  214  that define ball groove  210  may be slanted. Walls  214  may extend from radially outward surface  212  to a floor  216  of ball groove  210 . A width W 1  of ball groove  210 , as measured axially at radially outward surface  212 , may be greater than a width W 2  of ball groove  210 , as measured axially at floor  216 . In various embodiments, radially outward surface  212  may be slanted proximate a first axial end  220  of plug  158 , such that a diameter D 5  of plug  158 , as measured at radially outward surface  212 , decreases proximate first axial end  220 . In the secured position, illustrated in  FIG. 3B , first axial end  220  is located proximate (i.e., closer to) base  152 , as compared to a second axial end  222  of plug  158 . 
     Returning to  FIG. 3B , in the secured position, sleeve  156  may be in contact with socket  154 . Spring  160  may bias sleeve  156  toward, and into contact with, head  186  of socket  154 . In various embodiments, an interference surface  230  of sleeve  156  may be configured to force balls  180  into ball groove  210 , when sleeve  156  is in contact with head  186 . In accordance with various embodiments, interference surface  230  is slanted, or angled, such that a diameter of sleeve  156 , as measured at interference surface  230 , increases in the direction of head  186  of socket  154  (i.e., the diameter of a portion of interference surface  230  proximate head  186  is greater than the diameter of a portion of interference surface  230  distal head  186 ). An angle theta ( 0 ) of interference surface  230  may be selected such that interference surface  230  contacts balls  180 , when a portion of each ball  180  is located in ball groove  210  (i.e., when a portion of each ball  180  is located radially inward of radially outward surface  212  of plug  158 ) and/or when sleeve  156  is contacting head  186  of socket  154 . Angle theta ( 0 ) may be measured relative to a horizontal plane  232 . Horizontal plane  232  may be coplanar with radially outward surface  204  ( FIG. 4 ) of shaft  188  of socket  154  and/or parallel to a center axis of A-A′ of sleeve  156 . As used herein, the terms “axial” and “axially” refer to directions parallel to center axis A-A′, the terms “radial” and “radially” refer to directions toward and away from center axis A-A′, and the terms “circumferential” and “circumferentially” refer to directions about center axis A-A′. In accordance with various embodiments, interference surface  230  is non-parallel to center axis A-A′. In the secured position, balls  180  are located in ball groove  210  and generate an interference with walls  214  ( FIG. 5 ) of plug  158 . The inference between balls  180  and walls  214  restricts axial translation of plug  158  relative to base  152  and socket  154 , thereby coupling or securing plug  158  to base  152  and socket  154 . 
     With reference to  FIG. 6 , a cross-section view of releasable restraint  120  is illustrated, during evacuation slide deployment. In response to deployment (i.e., inflation) of evacuation slide  100  ( FIG. 1 ), first and second straps  126 ,  128  apply force  142 , in opposing directions, to releasable restraint  120 . The force  142  from first and second straps  126 ,  128  is applied to balls  180  via walls  214  ( FIG. 5 ) of ball groove  210 . The angle of walls  214  relative to floor  216  and the angle theta ( 0 ) of interference surface  230  are configured to cause balls  180  to translate in the radially outward direction and thereby force sleeve  156  to translate away from head  186 , in response to force  142  exceeding the biasing force applied by spring  160 . Radially outward translation of balls  180  causes a distance  238  between an axial end  240  of sleeve  156  and head  186  of socket  154  to increase. Translation of sleeve  156  away from head  186  decreases the axial distance between spring surface  164  and spring surface  166 , thereby causing spring  160  to compress. 
     With reference to  FIG. 7 , as the internal pressure within evacuation slide  100  continues to increase, the force  142  applied by first and second straps  126 ,  128  increases, thereby forcing balls  180  to translate out ball groove  210 . The radially outward translation of balls  180  forces sleeve  156  away from head  186  of socket  154 , thereby increasing distance  238 . In response to the entirety of each ball  180  being located radially outward of ball groove  210  (i.e., radially outward of radially outward surface  212  of plug  158 ), plug  158  may translate out plug channel  196 . Stated differently, releasable restraint  120  translates to the unsecured position, wherein plug  158  may decouple from base  152  and socket  154 , in response to removal of the interference between balls  180  and plug  158  (i.e. between balls  180  and walls  214  of ball groove  210 ). In various embodiments, sleeve  156  is configured such that a portion of sleeve  156  remains in contact with, and/or radially outward of, balls  180 , when releasable restraint  120  is in the unsecure deposition, to maintain balls  180  within ball openings  182 . 
     The force  142  associated with translating balls  180  radially outward (i.e., the force associate with separating or decoupling releasable restraint  120 ) may be adjusted by increasing or decreasing the spring constant of spring  160  and/or by increasing or decreasing the angle theta ( 0 ) of interference surface  230 , and/or by increasing or decreasing the angle of walls  214  relative to floor  216 . For example, increasing the angle theta ( 0 ) of interference surface  230  may decrease the force associated with separating releasable restraint  120  (i.e., with decoupling plug  158  from socket  154 ). 
     With reference to  FIG. 8 , a cross-section view of releasable restraint  120  with plug  158  separated from base  152  and socket  154  is illustrated. In response to removal of the interference between plug  158  and balls  180 , spring  160  may force sleeve  156  toward head  186 . Translation of sleeve  156  toward head  186  may force balls  180  radially inward, such that, at least, a portion of each ball  180  is located in plug channel  196 . In various embodiments, spring  160  may force sleeve  156  into contact with head  186  of socket  154 . In this regard, in response to removal of plug  158 , releasable restraint  120  translates or “resets” to a position configured to engage plug  158 , upon reinsertion of plug  158  into plug channel  196 . In this regard, releasable restraint  120  translates to a position, wherein balls  180  are located radially inward of radially inward surface  202  of socket  154 . 
     With reference to  FIG. 9 , securement of releasable restraint  120  is illustrated. In accordance with various embodiments, releasable restraint  120  may be translated to a secured position by inserting plug  158  into plug channel  196 . Radially outward surface  212  of plug  158  is configured to contact balls  180  and force balls  180  radially outward. In accordance with various embodiments, radially outward surface  212  being slanted proximate first axial end  220  of plug  158 , may facilitate the translation of balls  180  over plug  158  and toward interference surface  230 . Translation of balls  180  radially outward, in combination with the angle theta ( 0 ) of interference surface  230 , may force sleeve  156  away from head  186  of socket  154 , thereby increasing distance  238  and allowing balls  180  to continue translating radially outward. In response to balls  180  being radially aligned with ball groove  210 , spring  160  may force sleeve  156  toward head  186 . Translation of sleeve  156  toward head  186  may force balls  180  radially inward and into ball groove  210 . Locating balls  180  in ball groove  210  generates an interference between balls  180  and walls  214 , thereby coupling and/or securing plug  158  to base  152  and socket  154 . 
     Releasable restraints  120  employing spring  160  and slanted interference surface  230  to regulate the force associated with separation of releasable restraint  120  may allow for increased consistency with regard to releasable restraint  120  separating at the desired pressures. In this regard, releasable restraints  120  may allow for increased control of the deployment of evacuation slide  100  in  FIGS. 1 and 2A . Further, employing balls  180 , which reset after separation of plug  158 , allows releasable restraint  120  to be employed in subsequent evacuation slide deployments by reinserting plug  158  into plug channel  196  to re-secure releasable restraint  120 . In this regard, releasable restraint  120  is reusable. Reusing releasable restraint  120  may provide cost savings, particularly, with regard to slide testing and certification, wherein multiple deployments of evacuation slide  100  may be performed. 
     With reference to  FIGS. 10A, 10B, and 10C , a staged deployment of evacuation slide  100  from an aircraft  300  is illustrated. With reference to  FIG. 10A , a first stage of a deployment of evacuation slide  100  is illustrated, in accordance with various embodiments. A first (or initial) releasable restraint  120   a  may be coupled between a first strap  302  and a second strap  304 . First strap  302  may be attached to a first plug  158   a  of first releasable restraint  120   a . Second strap  304  may be coupled to a first base  152   a  of first releasable restraint  120   a . In various embodiments, first strap  302  may be attached to sliding surface  106  and second strap  304  may be attached to underside surface  108 . First releasable restraint  120   a  is configured to separate in response to an internal pressure of slide  100  exceeding a first threshold pressure. 
     With to reference to  FIG. 10B , a second stage of deployment of evacuation slide  100  is illustrated, in accordance with various embodiments. In response to the internal pressure of slide  100  exceeding the first threshold pressure, first plug  158   a  separates from first base  152   a  and first sleeve  156   a , thereby allowing evacuation slide  100  to unfold. A second releasable restraint  120   b  may be coupled between a third strap  306  and a fourth strap  308 . Third strap  306  may be attached to a second plug  158   b  of second releasable restraint  120   b . Fourth strap  308  may be coupled to a second base  152   b  of second releasable restraint  120   b . In various embodiments, third strap  306  may be attached to sliding surface  106  and fourth strap  308  may be attached to underside surface  108 . First strap  302  may be located closer to head end  102  as compared to third strap  306 . Second releasable restraint  120   b  may be configured to separate in response to an internal pressure of slide  100  exceeding a second threshold pressure. 
     With to reference to  FIG. 10C , a third stage of deployment of evacuation slide  100  is illustrated, in accordance with various embodiments. In response to the internal pressure of slide  100  exceeding the second threshold pressure, second plug  158   b  separates from second base  152   b  and second sleeve  156   b , thereby allowing evacuation slide  100  to further unfold. The second threshold pressure may be greater than the first threshold pressure. In various embodiments, a spring of second releasable restraint  120   b  is configured to bias second sleeve  156   b  and may have a spring constant that is greater than the spring of first releasable restraint  120   a . In various embodiments, an angle theta ( 0 ) of the interference surface of first sleeve  156   a  may be greater than an angle theta ( 0 ) of an interference surface of second sleeve  156   b.    
     A third releasable restraint  120   c  may be coupled between a fifth strap  310  and a sixth strap  312 . Fifth strap  310  may be attached to a third plug  158   c  of third releasable restraint  120   c . Sixth strap  312  may be coupled to a third base  152   c  of third releasable restraint  120   c . In various embodiments, fifth strap  310  may be attached to sliding surface  106  and sixth strap  312  may be attached to underside surface  108 . First strap  302  and/or third strap  306  may be located closer to head end  102  as compared to fifth strap  310 . 
     Third releasable restraint  120   c  may be configured to separate in response to an internal pressure of slide  100  exceeding a third threshold pressure. The third threshold pressure may be greater than the second threshold pressure. In various embodiments, a spring of third releasable restraint  120   c  is configured to bias third sleeve  156   c  and may have a spring constant that is greater than the spring of second releasable restraint  120   b . In various embodiments, an angle theta ( 0 ) of the interference surface of second sleeve  156   b  may be greater than an angle theta ( 0 ) of an interference surface of third sleeve  156   c.    
     Releasable restraints  120   a ,  120   b ,  120   c  employing springs and slanted interference surfaces to regulate the force associated with separation of releasable restraint may allow for increased consistency with regard to the releasable restraint separating at the desired pressures. In this regard, in addition to being reusable, releasable restraints  120   a ,  120   b ,  120   c  may allow for increased control of the deployment of evacuation slide  100 . 
     Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the disclosure. 
     The scope of the disclosure is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” It is to be understood that unless specifically stated otherwise, references to “a,” “an,” and/or “the” may include one or more than one and that reference to an item in the singular may also include the item in the plural. All ranges and ratio limits disclosed herein may be combined. 
     Moreover, where a phrase similar to “at least one of A, B, and C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C. Different cross-hatching is used throughout the figures to denote different parts but not necessarily to denote the same or different materials. 
     The steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Elements and steps in the figures are illustrated for simplicity and clarity and have not necessarily been rendered according to any particular sequence. For example, steps that may be performed concurrently or in different order are illustrated in the figures to help to improve understanding of embodiments of the present disclosure. 
     Any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact. Surface shading lines may be used throughout the figures to denote different parts or areas but not necessarily to denote the same or different materials. In some cases, reference coordinates may be specific to each figure. 
     Systems, methods and apparatus are provided herein. In the detailed description herein, references to “one embodiment”, “an embodiment”, “various embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments. 
     Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element is intended to invoke 35 U.S.C. 112(f) unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.