Abstract:
A lifting device to retrieve a marine vehicle comprises a lifting arms portion pivotally connected with a vehicle capture portion. The lifting arms portion and the vehicle capture portion rotate independently of each other. The vehicle capture portion comprises a capture connector having a probe for insertion into a latch opening in the vehicle to thereby attach the vehicle to the lifting device. The lifting arras portion further comprises two lifting arms and two vehicle pads for engaging the vehicle when it is captured. As the vehicle rolls during recovery operations, springs disposed between the vehicle capture portion and lifting arms portion dampen rotational motion. Lift line connections are provided on distal ends of the vehicle capture portion, and the lifting arms.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefore. 
    
    
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates generally to lifting devices and more specifically in one possible embodiment to a dampened one-axis pivoting lifting device for a multi-line lift configuration. 
     (2) Background of the Invention 
     In the maritime field, a lifting device is often used to grab or capture water vehicle such as unmanned underwater vehicles. The lifting device is typically a rigid frame that is clamped to the vehicle. The rigid frame provides lifting points to which multiple lift cables can be attached. Once the frame is secured to the underwater vehicle, a ship-borne crane lifts the water vehicle from the water. 
     However, the lifting process often takes place in a dynamic fluid environment that may comprise wind and waves that may cause the ship-borne crane and/or water vehicle to move relative to each other. In this environment, the water vehicle, which may be relatively heavy, is likely to experience rolling movement along the axis of the vehicle. 
     As the vehicle being lifted rolls in the water environment, some lines slacken while at some point during the roll, one or more other lines suddenly become taut. When these lift lines suddenly become taut, they must resist the entire weight and momentum of the vehicle that suddenly comes to bear. These dynamics can snap the lift lines during the recovery operation and/or cause damage to the vehicle as the frame engages the vehicle at stress points. Accordingly, this type of suddenly applied stress may be referred to herein as a “snap load”. 
     If a lift line breaks or if there is damage to the frame or vehicle due to a snap load, the lifting operation can be significantly prolonged. Equipment damage may occur to both the vehicle and lifting device. Moreover, breaking lines and/or equipment can potentially lead to unsafe environment for workers assisting in the capture of the underwater vehicle. 
     Consequently, those of skill in the art will appreciate the present invention, which addresses the above and/or other problems. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an improved lifting device for a multi-line lift configuration. 
     Another object of the present invention is to provide an improved lifting device for a multi-line lift configuration that significantly eliminates roll-induced snap loads created by a water vehicle during recovery in a dynamic fluid environment. 
     Another possible object of the invention is to provide a lifting device for a multi-line lift configuration that contains portions that rotate with respect to each other for spring dampening of vehicle movement during recovery in a water environment. 
     In accordance with the disclosure, the present invention provides a lifting device for a multi-point lift line configuration to capture a water vehicle. The lifting device comprises a vehicle capture portion and a lifting arms portion. The lifting arms portion may comprise two lifting arms correctable with at least two lift lines of the multi-point lift line configuration. At least one spring is connected to the two lifting arms. The lifting arms portion farther comprises at least two vehicle pads positioned for engagement with the vehicle whereby the spring is positioned between the vehicle capture portion and the lifting arms portion. The vehicle capture portion interfaces (rigidly) with the vehicle. So as the vehicle rolls, this portion rolls as well. When it rolls, the springs are compressed because the lifting arms portion is held level by the lift lines. In one preferred embodiment, the spring is positioned between the vehicle capture portion and the lifting arms portion. The vehicle capture portion interfaces (rigidly) with the vehicle. So as the vehicle rolls, this portion rolls as well. When it rolls, the springs are compressed because the lifting arms portion is held level by the lift lines. 
     A pivot connection is provided between the vehicle capture portion and the lifting arms portion. 
     In one embodiment, a capture connector further comprises a probe mounted to the vehicle capture portion that extends outwardly from the vehicle capture portion at a position for engaging the vehicle. 
     The vehicle capture portion may further comprise at least one lift line connection point positioned at a distal end from the lifting arms portion. The lift line connection point is operable for connection with at least one lift line of the multi-point lift line configuration. 
     The two lifting arms are positioned on the lifting arms portion to extend outwardly from the vehicle on opposite sides when in position with the capture connector secured to the vehicle. In one embodiment, the pivot connection permits relative rotation between the vehicle capture portion and the lifting arms portion only along one axis. The vehicle capture portion is preferably elongate in a direction of the one axis. 
     In another embodiment, a method is provided for making a lifting device for a multi-point lift line configuration to capture a vehicle. The method may comprise steps such as providing a vehicle capture portion with a capture connector operable to secure the vehicle capture portion to the vehicle and/or providing a lifting arms portion comprising two lifting arms that are connectable with at least two lift lines of the multi-point lift line configuration. 
     Other steps may comprise connecting a spring to each of the two lifting arms and pivotally connecting the vehicle capture portion to the lifting arms portion. 
     The method may further comprise positioning at least two vehicle pads for engagement with the vehicle in response to compressing the spring. 
     The method may further comprise providing that the pivot connection permits relative rotation between the vehicle capture portion and the lifting arms portion only along one axis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings constitute a part of this specification and include exemplary embodiments of the invention, which may be embodied in various forms. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate an understanding of the invention. 
         FIG. 1  is a perspective view depicting a vehicle being lifted from the water by a number of lift lines secured to a pivoting lifting device in accord with one possible embodiment of the present invention. 
         FIG. 2  is a perspective view of a pivoting lifting device with a lifting arms portion in a pivoted orientation with respect to a vehicle capture portion in accord with one possible embodiment of the present invention. 
         FIG. 3  is a perspective view of a pivoting lifting device in a zero-load position with a lifting arms portion in a non-pivoted orientation with respect to a vehicle capture portion in accord with one possible embodiment of the present invention. 
         FIG. 4A  is a cross-sectional diagram showing a water vehicle with attached pivoting lifting device with zero degrees of roll of the water vehicle and no pad contact in accord with one possible embodiment of the present invention. 
         FIG. 4B  is a cross-sectional diagram showing a water vehicle with attached pivoting lifting device with two degrees of roll in the direction of the arrow and initial pad contact with one pad in accord with one possible embodiment of the present invention. 
         FIG. 4C  is a cross-sectional diagram showing a water vehicle with attached pivoting lifting device with approximately five degrees of roll in the direction of the arrow. As noted above, the spring is not connected to the pad. 
         FIG. 4D  is a cross-sectional diagram showing a water vehicle with attached pivoting lifting device with approximately fifteen degrees of roll in the direction of the arrow and pad contact with partial spring compression in accord with one possible embodiment of the present invention. 
         FIG. 5  is a perspective view of a vehicle being lifted from the water by a pivoting lifting device in accord with one possible embodiment of the present invention. 
         FIG. 6  is a perspective view, partially in cutaway, illustrating the lifting arms portion of a lifting device in accord with one possible embodiment of the present invention. 
         FIG. 7  is a side elevational view of a pivoting lifting device secured to a water vehicle in accord with one possible embodiment of the present invention. 
         FIG. 8  is an elevational view, in section, of the mechanism for attachment to the water vehicle for the capture portion of the pivoting lifting device engaged with the water Vehicle as depicted in  FIG. 7  in accord with one possible embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Detailed descriptions of the preferred embodiment are provided herein. It is to be understood, however, that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or manner. 
     The need for this invention arises when lifting a mass out of a dynamic fluid environment with a lift-line configuration which allows the lifting device complete freedom to roll up to a certain point wherein from that point a high stress is applied that comprises a snap load that is suddenly applied to the lift-line configuration. 
     Turning to  FIG. 1 , multi-line capture system  100  comprises lifting device  10 , which is lowered onto vehicle  20 . The weight of vehicle capture portion  15  of lifting device  10  presses a probe into vehicle  20 , which then locks into vehicle  20 , as discussed hereinafter in reference to  FIG. 8 . Vehicle capture portion  15  preferably has a length sufficient to extend along a substantial portion of the vehicle, as shown in  FIG. 7 . 
     Multiple lift lines are utilized with lifting device  10 , which may comprise lift lines such as lines  12 ,  14 , forward lift lines  11 , and/or other lift lines and/or groups of lift lines. Lift line  12  attaches to arm  40  and lift line  14  attaches to arm  45 . Accordingly, lift lines  12 ,  14  may be utilized to prevent or resist rolling of vehicle  20 . 
     The lifting process requires that lift lines  12 ,  14  be slackened during capture, which allows lifting device  10  and vehicle  20  to begin to roll unrestrained. As the angle of the roil increases and/or as lift lines  12 ,  14  are tightened, the forces increase to resist rolling motion. However, in accord with the present invention, capture system  100  is designed to so that forces applied to the lift lines  12 ,  14  due to rolling of vehicle  20  increases more gradually. System  100  more gradually increases force to resist roll as one of lines  12  and  14  is more gradually tightened. In this way, the likelihood of sudden application of snap loads is greatly reduced or prevented. Vehicle  20  rolling motion is thereby better controlled without damage to lifting system  100  and/or the vehicle  20 . 
     A more in depth view of multi-line capture system  100  is depicted in  FIG. 5 . However, as shown, the vehicle is rotated to create tension in lift line  12 . When line  14  is tensioned, the vehicle should be rotated clockwise with respect to the lift arms  45 / 40 . Lift line arm  40  connects with lift line  12  via clevis hitch  65 . Lift line arm  45  connects with lift line  14  via clevis hitch  60 . In this scenario, as vehicle  20  rolls in a clockwise direction, vehicle pad  42  contacts vehicle  20  and force is gradually applied to lift line  14  through a spring-loaded connection between lift line arm  45  and vehicle capture portion  15 . Lifting device  10  also comprises pivot connection  35 , which allows lift line arms  40 ,  45  to pivot with respect to vehicle capture portion  15 . 
     Turning to  FIG. 2 , there is shown vehicle capture portion  15  and lifting arms portion  30  of lifting device  10 . Lifting arms portion  30  comprises lift-line interfacing arms  40 ,  45 . Lifting arms portion  30  is interconnected with vehicle capture portion  15  via pivot connection  35  that allows pivotal or rotational motion therebetween along a single axis in two directions as indicated by arrow  36 . In one embodiment, lifting arms portion  30  interfaces only with the corresponding lift lines  12 ,  14  connected at opposite ends thereof (see  FIG. 3 ) and pivot connection  35  of vehicle capture portion  15 . The vehicle capture portion  15  interfaces with the lifting arm (pivoting) portion and the vehicle. Vehicle capture portion  15  further comprises a capture connector  90  (see  FIG. 3 ), discussed hereinafter with respect to  FIG. 8 , which secures vehicle capture portion  15  to vehicle  20  to thereby capture vehicle  20 . Various types of appropriate capture connectors  90  known in the art may be utilized for connecting lifting device  10  to existing water vehicles. 
     In  FIG. 2 , vehicle capture portion  15  and lifting arms portion  30  are depicted in a pivoted position with respect to each other, which occurs when vehicle  20  rolls. Pivot connection  35  of lifting device  10  separates vehicle capture portion  15  and lifting arms portion  30  into two portions that can rotate independently of each other. Preferably, pivot connection  35  permits only rotation along a single axis that is parallel or generally parallel to axis  21  of vehicle  20  shown in  FIG. 7 . 
       FIG. 3  depicts lifting device  10  in a zero-load position, wherein vehicle capture portion  15  and lifting arms portion  30  are not pivoted with respect to each other, which occurs when vehicle  20  is in an upright position. In this embodiment, lifting device  10  is a three point device with essentially three lifting forces for application to three points  60 ,  65 , and  70  as indicated by respective lift lines  14 ,  12 , and  11 . However, more than three cables may be utilized even though in this embodiment lifting device  10  is shown as a three point lift device.  FIG. 1  shows a three point lift as well. In  FIG. 1 , line  16  is preferably a tag-line, used for side-to-side control, and not for lifting. Two forward lift lines  11  connect to the same lift-point. The present invention is intended to be a multipoint lifting device and is not limited to three lifting points and/or cables. For example only, another embodiment of the invention could comprise our lift lines and two pivoting arms. 
     Referring now to  FIG. 6 , springs  50  and  55  control the rotation of lifting device  10  by gradually slowing (or dampening) the rolling motion of vehicle  20  and thereby preventing snap loads suddenly being applied to lift-lines  12 ,  14 . As shown in  FIG. 6 , spring  55  is compressed, while spring  50  is not compressed. It will be noted that springs  50 ,  55  interface only between vehicle capture portion  15  and lifting arms portion  30 ; there are no springs between the pads  42 ,  47  (see, e.g.,  FIG. 4A ) and the lifting arms  40 ,  45 . In the example of  FIG. 5 , spring  55  is compressed, while spring  50  is not. 
     In  FIG. 6 , lifting arms portion  30  of lifting device  10  is depicted, partially in cut-away. Relative movement of lifting device  10  and vehicle  20  is controlled using springs  50 ,  55  to counteract rotation. Springs  50 ,  55  may comprise spring canisters or shock absorbers, as examples. Vehicle capture portion  15  (See  FIG. 2-3 ) connects with lifting arms portion  30  at pivot connection  35 . As vehicle capture portion  15  rotates relative to lift line arms  40 ,  45 , one of springs  50 ,  55  is compressed via one of spring rods  80 ,  85  depending on the direction of the roll. The compression of springs  50 ,  55  stores a large amount of energy. This energy buildup slows the roil of the vehicle being recovered and eliminates snap-line loading of the lift lines. In one non-limiting embodiment, the springs  50 ,  55  are connected via rods  80 ,  85  between the lifting arms portion  30  and the vehicle capture portion  15 . 
     The springs may be configured differently, may comprise more or fewer than two springs, and may or may not comprise rods  80 ,  85  as long as the springs are connected between lifting arms portion  30  and vehicle capture portion  15  so as to dampen the relative rotational movement therebetween. 
       FIGS. 4A  through  FIG. 4D  illustrate vehicle  20  at various degrees of roll with respect to lifting arms portion  30  that may be experienced during a recovery operation. The interaction of lifting arms  40 ,  45  and pads  42 ,  47  of lifting arms portion  30  is discussed in connection with increasing amounts of roll of the vehicle  30 . 
     Vehicle  20  is affixed to lifting device  10  by single point vehicle connection  90 , which is discussed in more detail below and illustrated in  FIG. 8 . The relative position of single point vehicle connection point  90  on vehicle capture portion  15  is also shown in  FIG. 3 . 
     In  FIG. 4A , vehicle  20  is not rolling; i.e., it is in a zero degree roll, upright and stationary. In this position, lift lines  12 ,  14  are both relatively slack or have even loads applied. Lift line arms  40 ,  45  are both at relative equal positions with respect to vehicle  20 . Vehicle pads  42 ,  47  are evenly spaced and may have little or no contact with vehicle  20 . 
     In  FIG. 4B , vehicle  20  experiences the first two degrees of an initial roll (e.g., in a clockwise direction as indicated by the arrow). Lift line  12  remains relatively slack, but lift line  14  may become more taught in reaction to the roll. Vehicle  20  makes contact with vehicle pad  42  and vehicle pad  47  may become, or remain, spaced away from vehicle  20 . 
     In  FIG. 4C , lifting arms portion  30  pivots sufficiently with respect to vehicle capture portion  15  to provide initial spring compression of spring  55  as vehicle  20  experiences roll, which in one embodiment may be in the general range of five to ten degrees. Vehicle pad  42  further applies pressure to vehicle  20  through spring  55  as lift line  14  becomes further tensioned. This tension causes spring  55  to compress and store energy to counteract rotation of vehicle  20  as discussed hereinbefore in reference to  FIG. 6 . 
       FIG. 4D  depicts vehicle  20  in an approximately fifteen degree roll. As the degree of the roll experienced by vehicle  20  increases, vehicle  20  will push against pad  42  with greater pressure and the tension will gradually increase on lift line  14 ; however, the countering force of spring  55  will also gradually increase and resist the roll of vehicle  20 . 
     It will be noted that if the roll was initiated in the opposite direction than that depicted by the arrow in  FIG. 4B , the descriptions above would hold true, except lift line  12  would be the line experiencing tension and pad  47  would initiate contact with vehicle  20 . 
     In  FIG. 7 , a side view is shown of lifting device  10  mounted to vehicle  20 . Vehicle capture portion  15  comprises single point vehicle connection  90 , which preferably is positioned near the center of gravity of vehicle  20  when the vehicle is captured. 
       FIG. 8  further depicts the details of one possible embodiment of single point vehicle connection  90  that is used to secure lifting device  10  to vehicle  20 . The invention is not limited to any particular connection or mounting to connect lifting device  10  to vehicle  20  and may utilize prior art single point vehicle connections that have been used to mount rigid frames to vehicles. In this embodiment, only a single point connection is provided between lifting device  10  and vehicle  20 . Probe  102  (see  FIG. 8 ) is secured to an underside of vehicle capture portion  15  as shown in  FIG. 7 . Referring to  FIG. 8 , probe  102  is inserted into latch opening  130  in vehicle  20 . Latch opening  130  is defined by first pawl  105  on one side and second pawl  110  on a side opposite first pawl  105 . Probe  102  further comprises shoulders  120 ,  115  which make contact with pawls  105 ,  110  respectively, after probe  102  is inserted into latch opening  130 . This connection secures vehicle  20  to lifting device  10  for safe recovery. 
     Accordingly, as discussed hereinbefore, the present invention prevents and/or significantly reduces the possibility of snap-line loading that was present with previous lifting devices. Pivotal lifting device  10  with spring loading eliminates snap-line loading between vehicle  20 , vehicle lift device  10 , and lift lines  12 ,  14 . 
     It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. 
     The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description only. It is not intended to be exhaustive nor to limit the invention to the precise form disclosed; and obviously many modifications and variations are possible in light of the above teaching. Such modifications and variations that may be apparent to a person skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.