Abstract:
A tiedown tensioner having a rotatably adjustable hook which can be operated in confined areas using a single hand. The tiedown tensioner facilitates the preferred positioning of the tensioning chain within the blind pocket, minimizes the potential energy for any given load, and dissipates the kinetic energy in a manner which minimizes the kickback movement of the tensioner.

Description:
This application claims the benefit of U.S. Provisional Application Ser. No. 62/169,179 filed Jun. 1, 2015, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to cargo tiedown tensioners used to secure cargo during transportation and, more particularly, to tensioners including both a hook for attachment to a fixed point and a pivotably-mounted chain block for releasably engaging a tensioning chain. 
     Cargo tiedown tensioners are used to secure cargo in aircraft, trains, trucks, ships, and the like, where it is necessary to prevent a shifting of such cargo during acceleration and/or movement of the transportation vehicle. In many applications, there is limited space for the operator to maneuver the tensioner, thereby hindering installation/removal of such device. To increase the ease of installation/removal of the tensioner, certain tiedown tensioners, such as the device disclosed in U.S. Pat. No. 8,646,820, now include a hook wherein the orientation of the hook can be adjusted by the operator. As will be recognized by those skilled in the art, the ability to orient the hook allows the operator to position the release handle of the tensioner in the most appropriate orientation for that particular installation. However, the prior art tiedown tensioners which include a rotatably adjustable hook suffer from the disadvantage that the operator is often required to use both hands to adjust the orientation of the hook. For example, the device disclosed in U.S. Pat. No. 8,646,820 requires the operator to simultaneously apply an axial tension force on opposing sides of the device to overcome a locking spring force before the hook can be reoriented. As already mentioned, the installation space in which the tensioner is installed is often quite limited, thereby rendering a device which may require two hands to re-orient the hook less than desirable. 
     The prior art discloses various chain tensioning and tiedown devices including the devices shown in U.S. Pat. Nos. 2,848,777, 2,903,767 and 4,850,768. These devices include a pivotably-mounted chain block having an entrance path to receive a tensioned segment of chain, and a blind pocket from which the slack (or free end) of the chain extends. There are, however, a number of problems associated with conventional tiedown devices, including those disclosed in the foregoing patents. In such devices, the precise placement of the chain in the blind pocket is important. If the chain link is not installed properly in the blind pocket (in contact with the bottom of the blind pocket), the force for release is increased in direct proportion to the increase in distance between the contact point and the bottom of the blind pocket. Accordingly, the operator must ensure the proper position of the chain link within the tensioner during securement of the cargo. 
     Certain applications require tiedown tensioners which are capable of being manually released under loads up to ten thousand (10,000) pounds. Potential energy at the pivot block increases as a function of the load. At the moment of release, potential energy in the tensioned chain is transformed into kinetic energy and transferred to the chain block. This kinetic energy results in the nearly instantaneous rotation of the chain block, such rotation typically being stopped by contact between the chain block and the rigid elements of the tensioner. Because of the nearly instantaneous transfer of the kinetic energy, the operator will likely still have his hand on the release lever, and may therefore be subjected to any kickback movement of the tensioner. 
     There is therefore a need in the art for a tiedown tensioner having a rotatably adjustable hook which can be operated in confined areas using a single hand. There is a further need in the art for a tiedown tensioner which facilitates the preferred positioning of the tensioning chain within the blind pocket, which minimizes the potential energy for any given load, and which dissipates the kinetic energy in a manner which minimizes the kickback movement of the tensioner. 
     SUMMARY OF THE INVENTION 
     The present invention, which addresses the needs of the prior art, provides a cargo tiedown tensioner for extending between a fixed point on a transportation vehicle and a tensioning chain. The tiedown tensioner includes: a) a rotatable hook subassembly for connecting the tiedown tensioner to the fixed point, the rotatable hook subassembly including a shaft having first and second ends, the hook subassembly further including a hook located at the first end of the threaded shaft; b) a support subassembly for transferring tension between the hook subassembly and the tensioning chain, the support subassembly including a rigid substantially closed body, the body including a slot extending along at least a portion of the length thereof; c) a tensioning subassembly cooperating with the rotatable hook assembly for taking up slack in the tensioning chain; d) an indexing mechanism for orienting the hook between predetermined positions, the indexing mechanism including a sliding block positioned inside of the body and configured to slide along at least a portion of the length thereof, the second end of the shaft being supported by the sliding block, the indexing mechanism further including a pivot lever movable between a first position wherein the shaft is rotatably fixed with respect to the sliding block and a second position wherein the shaft is rotatable with respect to the sliding block, at least a portion of the pivot lever being accessible via the slot to move the pivot lever between the first and second positions; e) a chain attachment subassembly connected to and supported by the body for securing the tensioning chain to the tiedown tensioner; and f) a release subassembly connected to the body and cooperating with the chain attachment subassembly, the release subassembly including a release lever movable between a locked position wherein the tensioning chain is retained within the chain attachment subassembly and an unlocked position wherein the tensioning chain is released from the chain attachment subassembly. 
     The present invention further provides a cargo tiedown tensioner for extending between a fixed point on a transportation vehicle and a tensioning chain. The tiedown tensioner includes: a) a rotatable hook subassembly for connecting the tiedown tensioner to the fixed point; b) a support subassembly for transferring tension between the hook subassembly and the tensioning chain; c) a tensioning subassembly cooperating with the rotatable hook assembly for taking up slack in the tensioning chain; d) a chain attachment subassembly connected to and supported by the body for securing the tensioning chain to the tiedown tensioner, the chain attachment subassembly including a pivot block for receiving the tensioning chain; e) a release subassembly connected to the body and cooperating with the chain attachment subassembly, the release subassembly including a release lever movable between a locked position wherein the tensioning chain is retained within the chain attachment subassembly and an unlocked position wherein the tensioning chain is released from the chain attachment subassembly; and f) a dynamic brake mechanism for dissipating the kinetic energy experienced by the tiedown tensioner at the moment of release, the dynamic brake mechanism including a pair of opposing preconfigured surfaces located on the pivot block and the body which engage upon release of the tiedown tensioner to provide a frictional braking surface. 
     The present invention further provides a cargo tiedown tensioner for extending between a fixed point on a transportation vehicle and a tensioning chain. The tiedown tensioner includes: a) a rotatable hook subassembly for connecting the tiedown tensioner to the fixed point; b) a support subassembly for transferring tension between the hook subassembly and the tensioning chain; c) a tensioning subassembly cooperating with the rotatable hook assembly for taking up slack in the tensioning chain; d) a chain attachment subassembly connected to and supported by the body for securing the tensioning chain to the tiedown tensioner, the chain attachment subassembly including a pivot block for receiving the tensioning chain, the pivot block rotatable about an axis O extending through the body, the pivot block including a blind pocket oriented parallel to the axis O and a sleeve oriented perpendicular to the axis O, the blind pocket defining a contact point B at the bottom thereof, the contact point B defining the point of contact between the tensioning chain and the pivot block and further defining a distance h with respect to the axis O, and wherein the axis of symmetry of the blind pocket extends through the axis O such that the tangent of an angle β defined between a perpendicular to a load force F L  and the axis of symmetry of the blind pocket is greater than the coefficient of friction between the pivot block and the tensioning chain whereby the tensioning chain is oriented to the contact point B and the distance h is minimized; and e) a release subassembly connected to the body and cooperating with the chain attachment subassembly, the release subassembly including a release lever movable between a locked position wherein the tensioning chain is retained within the chain attachment subassembly and an unlocked position wherein the tensioning chain is released from the chain attachment subassembly. 
     As a result, the present invention provides a tiedown tensioner having a rotatably adjustable hook which can be operated in confined areas using a single hand. The present invention further provides a tiedown tensioner which facilitates the preferred positioning of the tensioning chain within the blind pocket, minimizes the potential energy for any given load, and dissipates the kinetic energy in a manner which minimizes the kickback movement of the tensioner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 a    is a top perspective view of the tiedown tensioner of the present invention; 
         FIG. 1 b    is a bottom perspective view of the present tiedown tensioner; 
         FIG. 2  is an exploded perspective view of the present tiedown tensioner; 
         FIG. 2 a    is an exploded perspective view of the body of the present tiedown tensioner; 
         FIG. 2 b    is an enlarged detail taken from  FIG. 2 ; 
         FIG. 3  is an enlarged perspective view of the present tiedown tensioner with the body removed for clarity; 
         FIG. 4 a    is a view of the present tiedown tensioner showing the hook in a first orientation; 
         FIG. 4 b    is a view of the present tiedown tensioner showing the hook in a second orientation; 
         FIG. 4 c    is an enlarged detail showing the indexing mechanism in the locked position; 
         FIG. 4 d    is an enlarged detail showing the pivot lever of the indexing mechanism in the actuated position; 
         FIG. 5  is a sectional view of the present tensioner after release of the chain; 
         FIG. 6  is a detail taken from  FIG. 5 ; 
         FIG. 7  is a sectional view of the present tensioner at the moment of release of the chain; 
         FIG. 7 a    is an enlarged detail taken from  FIG. 7 ; 
         FIG. 8  is a sectional view of the present tensioner in the locked position; and 
         FIG. 8 a    is an enlarged detail taken from  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 a  and 1 b   , tiedown tensioner  100  of the present invention includes a rotatable hook subassembly  10  for connecting tiedown tensioner  100  to a fixed point on a transportation vehicle, a support subassembly  20  for transferring the tension between the hook subassembly  10  and a tensioning chain (not shown), a tensioning subassembly  30  for taking up slack in the tensioning chain, a positive locking mechanism  40  for securing tensioning subassembly  30  against inadvertent release and for allowing controlled operator increase/decrease of tension in the tensioning chain, an indexing mechanism  50  for orienting the hook between predetermined positions, a chain attachment subassembly  60  for engagement with the tensioning chain, a release subassembly  70  to allow the tensioning chain to be manually released and automatically separated from tensioner  100  in a one-handed operation, a positive chain lock mechanism  80  to prevent inadvertent detachment of the tensioning chain from tensioner  100 , and a dynamic brake mechanism  90  for dissipating the kinetic energy experienced by tensioner  100  at the moment of release. 
     Referring to  FIG. 2 , hook subassembly  10  includes a hook  2  having a threaded shaft  3  with a cylindrical end  4 , a latch  5 , a torsion spring  6  and a rivet  7 . As will be explained further herein, threaded shaft  3  allows for displacement of hook  2  to remove slack in the tensioning chain or to release tension in the chain without release/separation of such chain. 
     Referring to  FIG. 2 a   , support subassembly  20  includes a body  21  and an end plug  22 . End plug  22  includes a central aperture  23  extending therethrough and a recessed circular step  25  surrounding aperture  23 . Body  21  includes two opposing in-line apertures  24  perpendicular to aperture  23 , and which are located in the same plane with the axis defining aperture  23 . Body  21  is preferably a rigid substantially-closed body. In one preferred embodiment, body  21  is formed with a rectangular cross-section. The substantially-closed body design also allows for the attachment of end plug  22  to body  21  via welding or other suitable attachment methods such as swaging, soldering or press-fitting. Inasmuch as end plug  22  is formed with recessed circular step  25 , the manufacturing process is facilitated by forming end plug  22  as a separate component—and thereafter attaching the end plug to body  21 . The substantially-closed design of body  21  allows for the ready and satisfactory assembly of the various components of the present tensioner, while at the same time providing increased rigidity and strength (particularly against twisting loads) without significant increase in weight. Body  21  and end plug  22  are preferably formed from aluminum, titanium or other such lightweight materials, and are preferably manufactured via casting, forging, and/or machining processes. 
     Referring to  FIGS. 2 and 3 , tensioning subassembly  30  includes an internal nut  31  with concentric internal and external threads, a ratchet flange  32 , an adjustment nut  33  with a threaded aperture  35  sized to match the external threads of internal nut  31 , and two set screws  34  for securing adjustment nut  33  to internal nut  31 . Rotation of adjustment nut  33  in a first direction will remove the slack in the chain (thus increasing tension), while rotating adjustment nut  33  in the opposite direction will reduce tension in the chain. More particularly, rotation of adjustment nut  33  results in the displacement of hook  2  with respect to body  21 . Inasmuch as the tensioning chain (not shown) is fixed with respect to body  21 , the displacement of hook  2  either removes or increases the slack in the tensioning chain. 
     Referring to  FIGS. 2 and 3 , positive locking mechanism  40  automatically engages ratchet flange  32  upon completion of the tensioning operation. Positive locking mechanism  40  includes a push button rod  41  retained by a set screw  45 , a compression spring  42 , a leaf spring  43  and a plug  44  to support one end of the leaf spring. Leaf spring  43  is configured and biased to engage ratchet flange  32  of internal nut  31 , thereby locking hook  2  at a selected translated position. The operator can override the positive locking feature of leaf spring  43  by actuating push button rod  41 —which moves leaf spring  43  out of contact with ratchet flange  32 —thereby allowing the hook to be displaced with respect to body  21 —whereby the tension in the chain can be released without releasing/separating of the chain from the tensioner. 
     Referring to  FIGS. 2 to 4   d , indexing mechanism  50  allows for the one-handed rotation of hook  2  between at least two positions (preferably 180° apart) and includes a sliding block  51  positioned inside of body  21  of support subassembly  20 , a pivot lever  52  to lock the indexed position, a sleeve bearing  53 , a dowel pin  54  for connecting end  4  of hook  2  to sleeve bearing  53 , a dowel pin  55  and a compression spring  56  for biasing the shoulder of pivot lever  52  to the closed vertical position. More particularly, sleeve bearing  53  is formed with at least two opposing contact surfaces  58 . Contact surfaces  58  engage pivot lever  52 , thereby preventing rotation of bearing  53  within sliding block  51 . When pivot lever  52  is actuated (as shown in  FIG. 4 d   ), bearing  53  is free to rotate within sliding block  51 . Stated differently, hook  2  can be rotated upon actuation of pivot lever  52 . Once hook  2  is reoriented, pivot lever  52  is released and returns to the locked position via compression spring  56 , thereby locking hook  2  in its reoriented position. This can be accomplished by a single hand of the operator. 
     Referring to  FIGS. 2 b    and  3 , chain attachment subassembly  60  allows tensioner  100  to be quickly attached to a link of a tensioning chain, while also allowing automatic release of the tensioning chain upon operation of release assembly  70 . Chain attachment subassembly  60  includes a chain attachment pivot block  61  having a chain link blind pocket  62 , a slot  63  for the next chain link, and two bushings  64  which are press-fit into apertures  65  of pivot block  61 . Pivot block  61  includes two shoulders  66  oriented perpendicular to pocket  62  and parallel to apertures  24  (see  FIG. 2 a   ). A curved cam surface  67  is oriented eccentrically to the bottom surface of body  21 . 
     Referring to  FIGS. 2 and 3 , release subassembly  70  includes a release lever  71  and a support tube  72  extending through an elongated slot  79  of release lever  71  thereby allowing for both rotation and translation of release lever  71  with respect to body  21 . As shown, support tube  72  preferably includes a pair of notches  111  formed on opposing ends thereof. Support tube  72  preferably extends between the internal vertical walls of body  21 , with notches  111  contacting lips  26  of body  21  to prevent rotation of support tube  72  with respect to body  21 . Release subassembly  70  further includes a release lock  73  pivotably mounted on support tube  72  and a spring block  75  positioned between the legs of release lock  73 . Spring block  75  slidingly contacts tongue  112  of release lever  71 , thereby preventing rotation of slide block  75  with respect to release lever  71 . Release subassembly  70  further includes a compression spring  74  positioned between release lever  71  and spring block  75  for biasing release lever  71  to the locked position. Finally, release subassembly  70  includes a dowel pin  78  installed through opposing apertures  27  of body  21  for pivotably securing lever  71  and release lock  73  to body  21 . As best seen in  FIG. 3 , the legs of release lock  73  contact and engage shoulders  66  of pivot block  61  when the tensioner is in the locked position—thus securing pivot block  61  against rotation. During operation, the tensioning chain would remain engaged to pivot block  61  while in this orientation. 
     As best seen in  FIG. 8 a   , release lever  71  preferably includes at least one shoulder  113  which engages body  21  when the tensioner is in the locked position. As mentioned, compression spring  74  biases release lever  71  to this engaged and locked position. Before release lever  71  can be pivoted to the unlocked position (therefore releasing the tensioned chain), release lever  71  must first be translated a predetermined distance along body  21  against the bias of compression spring  74  to move shoulder(s)  113  out of engagement with body  21 . Such a design thereby provides a “safety mechanism” against inadvertent actuation of the release lever. 
     Referring to  FIGS. 2 and 3 , positive chain lock mechanism  80  includes a lock lever  81 , a dowel pin  82  for pivotably attaching lock lever  81  to release lock  73 , and a torsion spring  83  for maintaining contact between spring block  75  and the short shoulder of lock lever  81 . Once the tensioning chain is positioned in pivot block  61  and once release lever is moved to the locked position, lock lever  81  prevents the tensioning chain from detaching from the pivot block. It is only after the release lever is actuated that the lock lever is disengaged from the tensioning chain—thereby allowing the detachment of the tensioning chain from the pivot block. 
     Referring to  FIGS. 5 to 7   a , a dynamic brake mechanism  90  includes two preconfigured surfaces, namely curved cam surface  67  of pivot block  61  and a flat surface  91  formed on body  21 . After pivot block  61  is released, cam surface  67  tangentially merges with surface  91  thereby creating a frictional braking force sufficient to stop the rotation of pivot block  61  while at the same time limiting/eliminating the kickback movement of the tensioner. Of course, it is contemplated herein that the frictional braking arrangement between the pivot block and the body could be accomplished with different structure and/or utilize brake pads, or other wearable materials. 
     The preferred design of the geometry of the components of tensioner  100  is described hereinbelow with reference to  FIGS. 7 to 8   a . Pivot block  61  is configured to rotate around an axis O. Blind pocket  62  of pivot block  61  is oriented parallel to axis O, while slot  63  of pivot block  61  is oriented perpendicular to axis O. The bottom of blind pocket  62  defines a point of contact B between link 2 and the pivot block eccentric to axis O (distance h). A perpendicular line through the point of contact A between pivot block  61  and release lever  71  extends through the axis of rotation Z of the release lever. To release the lever, an operator applies a release force F R  at a distance L from axis Z. 
     It has been discovered herein that the proper positioning of the chain within the blind pocket (i.e., minimizing distance h which minimizes the potential energy transferred by the tensioning chain) can be accomplished without operator intervention if the geometry of pivot block  61  is configured in a predetermined manner. In other words, the minimum distance h between the load force F L  and the point of contact B is automatically accomplished without operator intervention. This will of course decrease the time and effort required to install the tensioner during a cargo securement operation. The geometry of pivot block  61  is therefore preferably configured such that the axis of symmetry of blind pocket  62  extends through axis O, and such that the tangent of the angle (“angle of friction β”) between a perpendicular to F L  and the axis of symmetry of blind pocket  62  is greater than the coefficient of friction between the pivot block and the chain links. 
     A vector of the load force F L  goes through axis O. The value of the load force is a variable sum of the preliminary tension applied by the operator and any increase/decrease in tension experienced during transportation. F L  is transferred through the contact of the toroid surfaces of links 1 and 2 to the pivot block at point B. Per Newton&#39;s first law, the pivot block is at rest when the resultant force (torque) of all external forces is equal to zero. Load force F L  can be presented as the sum of two vectors: Q R  (perpendicular to blind pocket  62 ) and Q S  (along the direction of blind pocket  62 ). Ignoring the weight of link 2, Q h  is substantially equal to F L . In other words, Q h =F L . 
     Q R  is the normal force which creates friction between the slot and link 2, thereby preventing link 2 from moving to the bottom of the blind pocket and reaching contact point B. Q R  can be represented by the following formula:
 
 Q   R   =F   L ×cos 20°.
 
     Q FR  is the friction force resisting the movement of link 2 to the bottom of the blind pocket. Q FR  can be represented by the following formula:
 
 Q   FR   =Q   R   ×K=F   L ×cos 20°× K,  
 
where K is the coefficient of friction between the pivot block and the chain.
 
     Q S  is the driving force oriented along the direction of the blind pocket which pushes link 2 to the bottom of the blind pocket. Q S  can be represented by the following formula:
 
 Q   S   =F   L ×sin 20°.
 
     If the driving force Q S  is equal to or smaller than the friction force Q FR , link 2 will not reach contact point B—and distance h will therefore be increased. Increasing distance h results in an increase in the kinematic energy transferred to the tensioner during the release of the tensioning chain. To ensure that link 2 reaches contact point B, it has been discovered herein that Q FR  should be selected to be smaller than Q S . 
     As a result, K≦tg 20°. Thus, to ensure the proper positioning of link 2, the coefficient of friction should be less than the tangent of the angle (i.e., angle β) between the perpendicular to the tensioning chain and the blind pocket when in the closed position. In one preferred embodiment, this angle has been determined to range from 12° to 30°. In one particularly preferred embodiment, the angle has been determined to be approximately 20°. 
     One goal of the present invention is to minimize the value of the release force. This is particularly relevant when the tensioner is used to secure larger loads. As shown below, the distance h is directly proportional to the value of the release force F R . Thus, any increase in distance h results in an increase in release force F R . According to Newton&#39;s first law, the pivot block remains at rest (in the locked position) when the resultant torque around axis O is equal to zero:
 
 F   N   ×H−Q   h   ×h= 0, where  Q   h   =F   L   [1].
 
Ignoring friction force F FR  for purposes of simplicity: F N =Q h ×h/H, and finally F N =F L ×h/H.
 
     The equation similar to equation [1] for the release lever is F FR ×D−F R ×L=0, where F FR =F N ×K1, where K1 is coefficient of friction for the contact between the release lever and the pivot block.
 
 F   N   ×K 1× D=F   R   ×L  from which  F   R   =F   N   ×K 1× D/L=F   L   ×h/H×K 1× D/L   [2]
 
To reduce the value of F R  in equation [2], we can consider the following options:
 
1) Reducing the coefficient of friction K1. This option is very limited in practice;
 
2) Reducing the D/L value by reducing the length of the D shoulder or by increasing the length the L shoulder. In practice, changing these values typically results in increased length/weight of the tensioner;
 
3) Reducing the h/H value by increasing the length of the H shoulder. In practice, changing this value typically results in increased length/weight of the tensioner; and
 
4) Reducing the h/H value by decreasing the length of the h shoulder. It is has been discovered herein that reducing the length of the h shoulder provides the most desirable and effective method of reducing the value of the release force.
 
     At the moment of release, the chain acts as a tensioned spring. The accumulated potential energy will immediately transform into kinetic energy—which will act to rotate pivot block  61 . At the moment of release, the pivot block begins to lose contact with the release lever at point A. The equation [1] transforms, and the resultant torque is no longer zero. The pivot block will be rotated by a driving torque resulting from load force F L  being applied through a distance h to the point B. This driving torque (Q h ×h or F L ×h) will be almost immediately transferred to the pivot block. The pivot block (together with links 1 and 2) will start to rotate in a clockwise direction (as viewed in  FIG. 8 a   ). Links 1 and 2 will undergo an acceleration sufficient to create a centrifugal force that drives the links out of the pivot block. As a result, the tensioning chain separates from the pivot block. As discussed above, curved cam surface  67  of the pivot block provides a braking surface which smoothly transform the transferred kinetic energy into heat energy as it contacts surface  91 . 
     It will be appreciated that the present invention has been described herein with reference to certain preferred or exemplary embodiments. The preferred or exemplary embodiments described herein may be modified, changed, added to or deviated from without departing from the intent, spirit and scope of the present invention, and it is intended that all such additions, modifications, amendments and/or deviations be included in the scope of the present invention.