Abstract:
A tensioning device for a fastening strap comprises a base and a lever; a spindle pivotally connecting the lever to the base and adapted to permit the strap to be wound therearound, the spindle having a first spindle component and a second spindle component which together define therebetween a gap adapted for passage of a portion of the strap; and at least one ratchet wheel disposed around the spindle for rotating in concert with the spindle and driven by the lever to rotate the spindle, wherein the gap has a variable width that can be narrowed to cause the first and second spindle components to clamp the strap.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to fastening devices, more particularly to ratchet buckles, strap tensioners, cargo restraining devices and the like used for tightening and tensioning a fastening strap for securing and restraining cargo loads or other objects. 
   2. Description of the Related Art 
     FIG. 1  shows a transport vehicle  11  carrying cargos or articles  12  secured by a plurality of fastening devices  2 . The articles  12  being transported, normally stacked side by side and one above the other, are restrained from undesired movement or toppling down by the fastening devices  12 . As shown in  FIGS. 2 and 3 , the fastening device  2  mainly comprises a lead strap  21 , a lashing strap  22 , a tightening and tensioning mechanism comprising a base  23  to which the lead strap  21  is attached and a lever  24  pivotally connected to the base  23  by a spindle formed by a pair of spindle components  25 , 26 , and a pair of ratchet wheels  27  disposed around both ends of the spindle and rotatable in concert with the spindle components  25 , 26  when driven. A free end of the lashing strap  22  is attached to the spindle so as to be wound therearound. The ratchet wheels  27  each have a central hole which is separated into two semicircular openings, and the spindle components  25 , 26  are of semicircular cross section corresponding to the shape of the openings. The spindle components  25 , 26  are inserted into said openings, respectively, thus defining therebetween a gap for passage of a portion of the lashing strap  22 . The lever  24  has a ratchet drive plate  241  for engaging and driving the ratchet wheels  27  to rotate in the winding direction of the lashing strap  22  when the lever  24  is pulled away from the base  24 , and which is resiliently releasable from the ratchet wheels  27  when the lever  24  is pushed forward to the base  23  in the unwinding (reverse) direction, and the base  23  has a stop  231  that prevents the ratchet wheels  27  from rotating in the unwinding direction of the lashing strap  22  and that may be resiliently released from the ratchet wheels  27  when the ratchet wheels  27  are rotated in the winding direction. By such construction, the spindle components  25 , 26  can be rotated step by step to thereby incrementally shorten and tension the lashing strap  22 . 
   In use, the articles  12  are preliminarily fastened with the lead and lashing straps  21 , 22 , and then the lever  24  is repeatedly pulled back and forth, which causes the ratchet wheels  27  to drive the spindle components  25 , 26  to rotate in the winding direction of the lashing strap  22  thus incrementally shortening the length of the lashing strap  22 . Accordingly, the lead and lashing straps  21 , 22  maintain the fastening tension and will not be loosened by the swaying motion of the transport vehicle, such that the objective of tightly fastening and restraining the articles  12  is achieved. 
   However, because the spindle components  25 , 26  are spaced-apart at a fixed distance due to the constraints of the ratchet wheels  27 , the final angle/position of the spindle components  25 , 26 , after being rotated in the winding direction to shorten the length of the lashing strap  22  for tensioning the articles  12 , is unpredictable and usually only one of the spindle components  25 , 26  (i.e., the spindle component  26 ) bears the stress exerted along the tensioning direction. Even if both spindle components  25 , 26  bear the stress, the areas subjected to the stress are confined to the two edges  251 , 261  of the spindle components  25 , 26 , respectively. Such stress concentration causes insufficiency in structural strength and easily predisposes the affected parts to twisting and deformation and even so far as causing fracture or breakage. 
   SUMMARY OF THE INVENTION 
   Therefore, in the light of the above-described disadvantages encountered in the prior art, a main object of the present invention is to provide a tensioning device for a fastening strap in which the stress generated from the tensioned cargo loads or objects can be dispersed thereby enhancing the structural strength of the device. 
   Accordingly, the present invention provides a tensioning device for a fastening strap which comprises a base and a lever; a spindle pivotally connecting the lever to the base and adapted to permit the strap to be wound therearound, the spindle having a first spindle component and a second spindle component which together define therebetween a gap adapted for passage of a portion of the strap; at least one ratchet wheel disposed around the spindle for rotating in concert with the spindle and driven by the lever to rotate the spindle, wherein the gap has a variable width that can be narrowed to cause the spindle components to clamp the strap. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the present invention will become apparent in the following detailed description of a preferred embodiment with reference to the accompanying drawings, in which: 
       FIG. 1  shows the manner in which a conventional fastening device is used to secure cargo loads or articles on a transport vehicle; 
       FIG. 2  is a perspective view showing the conventional fastening device with a tightening and tensioning mechanism for a lashing strap; 
       FIG. 3  is a sectional view showing the conventional fastening device shown in  FIG. 2 ; 
       FIG. 4  is an exploded, perspective view of a tensioning device for a fastening strap according to a preferred embodiment of the present invention; 
       FIG. 5  is a perspective view of the preferred embodiment in the assembled form; 
       FIG. 6  is a partially sectioned view showing the spindle of the tensioning device rotated in an unwinding direction to loosen the fastening strap; and 
       FIG. 7  is the same view as  FIG. 6  but showing the spindle rotated in a winding direction to tighten the fastening strap. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to  FIGS. 4 and 5 , a tensioning device for a fastening strap according to a preferred embodiment of the present invention generally comprises a base  41  to which a first, or lead, strap  31  is attached and a lever  42  pivotally connected to the base  41  by a spindle  6 , around which a free end of a second, or lashing, strap  32 , is wound. The base  41  has a pair of lugs  412  each formed with a base spindle hole  411 , and the lever  42  has a pair of ears  422  aligned with said lugs  412 , respectively, each being formed with a lever spindle hole  421 . Two ratchet wheels  5  are disposed around the spindle  6 , each of which is between one the base spindle holes  411  and one of the lever spindle holes  421 . The spindle  6  extends into the base and lever spindle holes  411 , 421  and the ratchet wheels  5 . The ratchet wheels  5  rotate in concert with the spindle  6  when driven by the lever  42  to rotate the spindle  6 . 
   The spindle  6  includes a first spindle component  61  and a second spindle component  62  both of which, in the illustrated embodiment, have a semicircular cross section, the cross section of the first spindle component  61  being larger than that of the second spindle component  62 . The second spindle component  62  is formed with two shoulders  623  and two constricted end sections  621  respectively extending from the shoulders  623  and each having a rectangular cross section. Each ratchet wheel  5  has a first opening  511  that is segmental and substantially corresponds to the cross section of the first spindle component  61 , for receiving immovably therein the first spindle component  61 , and a second opening  512  in communication with the first opening  511  for receiving movably the second spindle component  62 , specifically, one of the constricted end sections  621 . The second opening  512  has an oblong shape longer than the rectangular cross section of the respective constricted end section  621  of the second spindle component  62  and extending in a radial direction, the first opening  511  extending in a chordal direction perpendicular to the radial direction. Each constricted end section  621  of the second spindle component  62  is inserted into the respective base and lever spindle holes  411 , 421  and positioned in the second opening  512  of the respective ratchet wheel  5 . The second spindle component  62  is displaceable within the respective second opening  512  of the ratchet wheels  5 . Accordingly, the second spindle component  62  is movable toward the first spindle component  61  within the confines of the second openings  512 . Each ratchet wheel  5  further has two protrusions  513  that confine the second opening  512  and that extends into the respective base or lever spindle holes  411 , 421 . In this embodiment, each protrusion  513  extends into the respective lever spindle hole  421  and is slidable along an edge bounding the respective lever spindle hole  421  when the ratchet wheels  5  rotate, so that the ratchet wheels  5  are prevented from displacing in a direction transverse to the axis of the spindle  6 . Preferably, each ratchet wheel  5  is made up of two ratchet plates  51 . 
   Two elastic elements  65  (only one is shown) are disposed between the first and second spindle components  61 , 62  to bias the first and second spindle components  61 , 62  to move away from each other, thereby forming a gap  60  therebetween for passage of a portion of the lashing strap  32 . Two sleeves  63  are disposed around the first spindle component  61  and the constricted end sections  621  of the second spindle component  62 . There are two pins  64  (only one is shown), each being inserted into the first spindle component  61  and the respective constricted end section  621  and extending through the gap  60  and into the respective sleeve  63 . Each elastic element  65  is coiled around the respective pin  64 . By their restoring force, the elastic elements  65  urge the first and second spindle components  61 , 62  to separate in the absence of external force applied thereto. 
   The gap  60  defined between the first and second spindle components  61 , 62  has a variable width that can be narrowed to cause the spindle components  61 , 62  to clamp the lashing strap  32 , as will be explained in more detail below. 
   When the present invention is used to secure a cargo load or object, the lead strap  31  and the lashing strap  32  are preliminarily fastened over the load as similarly shown in  FIG. 1 . The lever  42  is then repeatedly raised and lowered relative to the base  41  to drive the ratchet wheels  5  to rotate the spindle  6  in the winding direction and to wind the lashing strap  32  around the spindle  6 , thereby incrementally shortening the length of the lashing strap  32  and incrementally tensioning and tightening the lashing strap  32 . The lead strap  31  and lashing strap  32  are retained in a tensioned condition that restrains the cargo load even in the swaying motion of the transport vehicle, so that the objective of tightly securing a load is achieved. 
   Referring to  FIGS. 4 ,  6  and  7 , as the lashing strap  32  is wound around both the first and second spindle components  61 , 62  by actuation of the lever  42 , the second spindle component  62 , with the constricted end sections  621 , is urged to overcome the biasing force of the elastic elements  65  within the second openings  512  of the ratchet wheels  5  to move toward the first spindle component  61  in the axial direction of the pins  64 , thus narrowing and closing the gap  60  and clamping the portion of lashing strap  32  between the first and second spindle components  61 , 62 . The spindle components  61 , 62  thus act as one unitary body. 
   When the first spindle component  61 , after tensioning the lashing strap  32 , is subjected to stress exerted in the tensioning direction, since the cross section of the first spindle component  61  is larger than that of the second spindle component  62 , the first spindle component  61  which is more sturdy in its overall structure provides sufficient structural strength to bear the pulling force of the lashing strap  32 . When the second spindle component  62  is subjected to stress exerted in the tensioning direction, since the second spindle component  62  moves to the first spindle component  61  and becomes integrated with the first spindle component  61  due to the tensioned lashing strap  32  being wound around the two, the first and second spindle components  61 , 62  becomes a unitary body with increased structural strength to withstand the tensional forces. In addition, the unitary body provides an increased contact area between the spindle  6  and the lashing strap  32  so that the tensional forces are spread over and shared by the first and second spindle components  61 , 62 . 
   It can be appreciated, from the description above, that the tensioning device of the present invention has the following advantages and effects: 
   By the construction of the gap  60  which is variable in width, the first and second spindle components  61 , 62  are combined closely through the tensioned lashing strap  32  thus forming a unitary body, and the acting forces exerted by the lashing strap  32  are distributed over both the first and second spindle components  61 , 62 , such that the first and second spindle components  61 , 62  share the acting forces. Further, in conjunction with the different size arrangement of the first and second spindle components  61 , 62 , the contact area of the spindle  6  to contact the lashing strap  32  is enlarged, which in turn enhance the overall structural strength of the spindle  6 , thus extending the useful life of the device. 
   While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that the present invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.