Abstract:
Actuations systems in which pulley systems may be used as redundant (back-up) mechanisms are described. The systems provide mechanical advantage, especially useful when manual input is required to deploy a back-up mechanism. A pulley may be integrated into a clevis, a cable routed about the pulley, and one end of the cable made stationary, causing the pulley to counterbalance approximately twice the input force provided.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to actuation systems and more particularly, but not necessarily exclusively, to manual, redundant (back-up) actuators of inflatable, buoyant emergency equipment such as life rafts, flotation devices, or evacuation slides. 
       BACKGROUND OF THE INVENTION 
       [0002]    U.S. Pat. No. 8,079,547 to Rivault, et al., describes exemplary flotation systems especially useful for helicopters and other vessels. The flotation systems may include both floats and life rafts if desired. A single actuator may cause inflation of both a float and a raft; alternatively, separate activators may be employed. Noted as well in the Rivault patent is that “automatic or manual activators could be used for redundancy or back-up purposes.” See Rivault, col. 2,11. 18-19. 
         [0003]    Commonly-owned U.S. Pat. No. 7,644,739 to Vezzosi, et al., discloses examples of actuators for inflatable structures. One type of existing main actuation system identified in the Vezzosi patent includes a container of pressurized gas and “a cable and pulley system routed through [an] aircraft.” See Vezzosi, col. 1,1. 30. According to the Vezzosi patent, “[w]hen a pull handle or similar device associated with the system is activated,” a valve opens and “the pressurized gas is discharged from the container and into the life raft causing its rapid inflation.” See id. at 11. 31-35. No discussion of using a pulley system to obtain mechanical advantage is included, however. Nevertheless, the contents of the Rivault and Vezzosi patents are incorporated herein in their entireties by this reference. 
       SUMMARY OF THE INVENTION 
       [0004]    Undeveloped to date are any actuation systems in which a pulley system is used as a redundant or back-up mechanism for a main pneumatic actuator such as a piston. Presently, any manual back-up for a failed main actuator typically is attached directly to an output load, such as a clevis, which in turn is connected to a source of inflation gas. This sort of direct attachment requires maximum input force to be used, as no mechanical advantage is available. By contrast, utilizing the back-up pulley system of the present invention gains mechanical advantage, thus reducing the input force necessarily provided manually. 
         [0005]    In at least one embodiment of the invention, a (preferably low-friction) pulley is integrated into the clevis. A cable may be attached or otherwise fixed at a first end portion to a stationary anchor point and at a second end portion to an input source. In between the two end portions, the cable may be routed around the pulley and, beneficially, along a guide surface that itself preferably is either a low-friction surface or a secondary pulley. 
         [0006]    As the input source applies tension to the cable, the first end portion remains stationary at the anchor point. Consequently, the pulley must counterbalance twice the input load because the cable is tensioned on segments on either side of the pulley. The counterbalancing force is transmitted through the pulley to the clevis and thence to the output load in communication with the clevis. Preferably the output load will be a valve or other device associated with a source of inflation gas, although the output load is not limited to such devices. Also preferably, positioning of the anchor point and guide surface are such that the segments of the cable on either side of the pulley remain parallel (or substantially so) through much (or all) of the piston stroke. 
         [0007]    It thus is an optional, non-exclusive object of the present invention to provide redundant (back-up) mechanisms for actuators. 
         [0008]    It is another optional, non-exclusive object of the present invention to provide back-up mechanisms employing one or more pulleys. 
         [0009]    It is also an optional, non-exclusive object of the present invention to provide manually-operated back-up mechanisms in which mechanical advantage is gained. 
         [0010]    It is a further optional, non-exclusive object of the present invention to provide back-up mechanisms in which an object may be inflated when the mechanism is utilized. 
         [0011]    It is an additional optional, non-exclusive object of the present invention to provide back-up mechanisms in which a cable may be routed around a pulley, with one end portion of the cable fixed in position and the other end portion directly or indirectly connected to an input source. 
         [0012]    It is, moreover, an optional, non-exclusive object of the present invention to provide back-up mechanisms in which portions of the cable on opposite sides of the pulley remain generally parallel as an output load moves. 
         [0013]    Other objects, features, and advantages of the present invention will be apparent to those skilled in the relevant art with reference to the remaining text and the drawings of this application. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a schematic, partially cut-away representation of portions of a redundant or back-up mechanism of the present invention. 
           [0015]      FIG. 2  is a pictorial, partially-schematicized representation of portions of a mechanism generally consistent with  FIG. 1 . 
           [0016]      FIG. 3  is a simplified block diagram of main and back-up actuator mechanisms for an inflatable object. 
           [0017]      FIG. 4  is a schematic, non-cutaway version of the portions of the mechanism of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Illustrated in  FIGS. 1 and 4  are portions of back-up mechanism  10  of the present invention. Mechanism  10  may include cable  14  (shown in dotted lines in  FIG. 1 ) and pulley system  18 . Although clevis  54  is a preferred connection for use with mechanism  10 , other means of connecting to an outlet load may be employed instead. Also shown in  FIGS. 1 and 4  is piston  26 . In general, tensioning of cable  14  causes compression of piston  26  so as to displace clevis  54 . In turn, displacement of clevis  54  causes change in an output load. One preferred output load is an output cable  22  connected to a valve or other means for allowing gas to communicate with an inflatable object such as, but not limited to, a life raft or other flotation device. 
         [0019]    As depicted in  FIG. 1 , first end portion  30  of cable  14  may be attached or otherwise connected to an anchor at a location such as anchor point  34 . The anchor may be any object, device, structure, etc., adequate to fix the position of first end portion  30  notwithstanding movement of second end portion  38  of cable  14  (see  FIG. 2 ). By contrast, second end portion  38  is directly or indirectly connected to input source  42 . In practice, input source  42  may be a handle configured to be grasped by a human hand, although other equipment may comprise input source  42  additionally or instead. 
         [0020]    Pulley system  18  may include at least wheel  46  and pin  50 . Wheel  46  is configured with groove  52  or otherwise so as to receive cable  14  along a portion of its circumference. Alternatively, if wheel  46  is not circular, it may receive cable  14  along a portion of its periphery. Wheel  46  further may be configured to rotate about pin  50 , although such rotation is not necessary for successful operation of embodiments of mechanism  10  consistent with  FIGS. 1-3 . Although a non-rotatable wheel  46  arguably would not then be part of a “pulley system” in common parlance, it remains within the definition of pulley system as used herein. 
         [0021]    At least portions of mechanism  10  advantageously may be integrated with piston  26 . As illustrated in  FIG. 1 , for example, clevis  54  may be integral with piston  26  as part of a main actuation system. Clevis  54  may extend piston  26  and include an internal post  58  about which output cable  22  is fitted. If piston  26  is compressed automatically, it will cause clevis  54  (and post  58 ) to move in turn. Movement of post  58  will cause output cable  22  to displace linearly and thereby act upon the output load. By adding an integrated pulley system  18 , manual back-up may be provided integrally to compress piston  26  should the automatic main actuator fail to do so. 
         [0022]    Also illustrated in  FIG. 1  is guide surface  62  for cable  14 . Guide surface  62  is optional; if present, it preferably is a low-friction surface or a secondary pulley. Likewise if present, guide surface  62 , as well as anchor point  34 , preferably are offset from clevis  54  sufficiently to allow segments  66  and  70  of cable  14  adjacent pulley system  18  to remain parallel (or substantially so) throughout the stroke of piston  26 . 
         [0023]      FIG. 3 , finally, schematically represents a highly-simplified arrangement  74  including back-up mechanism  10 . As noted earlier, mechanism  10  may be deployed together with main actuator  78  and inflatable object  82 , which may be connected to or otherwise associated with vessel V such as (but not limited to) a fixed- or rotary-wing aircraft. Main actuator  78  is configured to communicate with inflatable object  82  so as to provide inflation fluid thereto. Back-up mechanism  10  also is configured in this manner and may be used to inflate object  82  should main actuator  78  fail to do so. 
         [0024]    When input source  42  is active (as when someone pulls on second end portion  38 ), cable  14  tenses. Segments  66  and  70  become taut, after which they apply force to wheel  46 . Wheel  46  thus must counterbalance twice the input loading, providing a mechanical advantage of up to one hundred percent as compared to a direct attachment of cable  14  to clevis  54 . 
         [0025]    The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of the present invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of the invention.