Abstract:
A tie down device comprised of a tie down strap and a ratchet take-up device, with the ratchet being suitable for taking up the tie down strap in order to change the effective length of the strap for use with different sized loads and to create tension over a load when securing it, with the tie down strap having a relatively long inelastic proximate portion and a relatively short elastic distal portion; such that the inelastic portion of the strap maintains tension on a load being secured and the elastic portion of the strap serves as an automatic re-tensioning means if the load shifts.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates generally to the field of tie down devices, and more particularly to tie down straps used with ratchet devices. 
     2. Description of Prior Art 
     Tie down devices are well known in the art, as are tie down straps used with ratchet devices. Typical tie down strap/ratchet devices employ a substantially inelastic strap and a ratchet take-up device, with a first engagement device located at the distal end of the strap and a second engagement device located proximate to the ratchet. The engagement devices are typically hooks. The strap is taken up by the ratchet and wound about a drum, which shortens the effective length of the strap. Gearing in the ratchet prevents the drum from counter-rotating, thus maintaining the strap length under tension. A release mechanism built into the ratchet disengages the gearing and allows the strap to be unwound from the drum, lengthening the effective length of the strap. In use, the strap is placed over the object or objects to be tied down, the engagement devices are engaged with fixed objects, then the ratchet is used to take up the slack in the strap until the strap is taut over the object or objects intended to be secured. This configuration provides a practical device for securing differently sized objects, since the length of the strap can be as long or as short as needed, within its physical constraints. 
     While the above-described tie down strap/ratchet device adequately secures a stationary load, if the load is jostled during transport even slight relative movement of the object or objects being secured can result in a slackening of the tension of the strap. See  FIGS. 2A-2C . Since the strap is substantially inelastic, any slack introduced to the strap remains and presents a danger of the load becoming less secure. Further jostling may introduce ever more slack to the strap until the load is no longer secured. 
     Another common tie down device uses an elastic elongate cord having an engagement device at each end. This is typically known as a bungee cord. A bungee cord is used by being placed over the object or objects to be tied down, then the engagement devices are engaged with fixed objects. Because the length of the bungee cord is less than the distance between the fixed objects, the cord is stretched over the object or objects intended to be secured, and the tension in the cord provides the securing means. 
     While the above-described bungee tie down device is capable of overcoming slack introduced through jostling of the load, it also has disadvantages. Because the bungee cord is of a fixed length, for any given load only a specially sized bungee cord will be adequate. This necessitates multiple bungee cords for different sized loads. Also, since the entire length of the bungee cord is elastic, even a taut bungee cord presents an unwanted amount of stretch. Thus, where slight jostling might not have created movement in a load secured by an inelastic strap, that same degree of jostling will, even if only temporarily, allow movement in the load. While the bungee cord will immediate retract to take up the slack, the total amount of movement of the load may be unacceptable and eventually result in dangerous shifting of the load. 
     The foregoing illustrates that there is a need in the art for an improved tie down device which incorporates the benefits of both typical tie down systems while avoiding their disadvantages. 
     It is therefore an objective of the present invention to provide a tie down device that is suitable for securing a load. 
     It is a further objective of the present invention to provide a tie down device that has a changeable effective length so that it may be used on different sized loads. 
     It is yet a further objective of the present invention to provide a tie down device that has a strap which is substantially inelastic for most of its length to minimize movement of a secured load. 
     It is yet a further objective of the present invention to provide a tie down device that has a strap which is substantially elastic for a short portion of its length to allow for automatic re-tensioning of the strap across a load which has shifted slightly. 
     It is yet a further objective of the present invention to provide a tie down device that is inexpensive to manufacture. 
     It is yet a further objective of the present invention to provide a tie down device that is easy to use. 
     Other objectives of the present invention will be readily apparent from the description that follows. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention is directed to a tie down device using a tie down strap and a ratchet take-up device. The strap and ratchet are substantially similar to traditional tie down devices using a tie down strap and a ratchet take-up device except that a small portion of the distal end of the strap is made of an elastic material. The elastic portion of the strap may be capable of stretching to several times its unstretched length, but only if a substantial force is applied to it. Like prior art devices, the device of the present invention also has engagement components at the ends to secure the device to fixed anchor points. 
     The device of the present invention is used in the same manner as the prior art devices, namely, the strap is placed over the object or objects to be tied down, the ends are engaged with fixed anchor points, then the ratchet is used to take up the slack in the strap until the strap is taut over the object or objects intended to be secured. See  FIG. 3A . However, with the present invention, the ratchet is continued to be used to stretch the elastic portion of the strap to between about half of its total stretchable length and one hundred percent of its total stretchable length. In the preferred embodiment the elastic portion of the strap is stretched to substantially one hundred percent of its total stretchable length. This introduces a self-adjusting mechanism to the device while in use. Thus, if the load is jostled (see  FIG. 3B ) the elastic portion of the strap will retract to retain tension on the load (see  FIG. 3C ). If the load alters its position slightly, the elastic portion will retract somewhat more, again maintaining tension on the load. It is important to remember that the elastic portion of the strap of the present invention requires a great deal of force to be stretched; therefore, under slight jostling there would be no appreciable changes in the length of the strap and it would act identically to straps in the prior art. But where the force is sufficiently great that it would have dislodged the load if secured by a prior art strap, the strap of the present invention will instead automatically reset the tension through refraction of its elastic portion. 
     Other features and advantages of the invention are described below. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective top view of one embodiment of the tie down device of the present invention. 
         FIG. 1B  is a perspective top view of another embodiment of the tie down device of the present invention. 
         FIG. 2A  is a stylized rear view of a truck carrying a load secured with a ratchet tie down device of the prior art. 
         FIG. 2B  is a stylized rear view of the truck depicted in  FIG. 2A  after it has hit a bump in the road, resulting in the load being jostled and slightly repositioned under the tie down strap of the tie down device of the prior art. 
         FIG. 2C  is a stylized rear view of the truck depicted in  FIG. 2A  showing how the load has shifted and the tie down strap of the tie down device of the prior art is now slack. 
         FIG. 3A  is a stylized rear view of a truck carrying a load secured with a ratchet tie down device of the present invention. 
         FIG. 3B  is a stylized rear view of the truck depicted in  FIG. 3A  after it has hit a bump in the road, resulting in the load being jostled and slightly repositioned. 
         FIG. 3C  is a stylized rear view of the truck depicted in  FIG. 3A  showing how the load has shifted, yet the tie down strap remains taut. The elastic portion of the strap is shown to have contracted somewhat in response to the slight repositioning of the load. 
         FIG. 4A  is a perspective view of the embodiment of the strap and engagement member of the present invention depicted in  FIG. 1A  with the elastic portion of the strap in its unstretched state. 
         FIG. 4B  is a perspective view of the embodiment of the present invention depicted in  FIG. 4A  with the elastic portion of the strap in its stretched state. 
         FIG. 5A  is a perspective view of the embodiment of the strap and engagement member of the present invention depicted in  FIG. 1B  with the elastic portion of the strap in its unstretched state. 
         FIG. 5B  is a perspective view of the embodiment of the present invention depicted in  FIG. 5A  with the elastic portion of the strap in its stretched state. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1A  depicts one embodiment of the tie down device  1  of the present invention. The basic tie down device  1  comprises a strap  100 , a ratchet mechanism  200 , and an engagement member  300 . A preferred embodiment further comprises an anchor strap  150  and a second engagement member  310 . 
     The strap  100  of the present invention is elongate, substantially flat, and flexible, and is suitable for being used with a ratchet mechanism  200 . The strap  100  has a length, a substantially uniform width, a proximate end  104 , a distal end  106 , an inelastic portion  120 , and an elastic portion  110 . 
     The inelastic portion  120  of the strap  100  has a length, a width, a proximate end  124 , and a distal end  126 . The inelastic portion  120  of the strap  100  is located at the proximate end  104  of the strap  100  and its length comprises the greater portion of the overall length of the strap  100 . In the preferred embodiments the length of the inelastic portion  120  of the strap  100  comprises at least ninety percent of the overall length of the strap  100 . The inelastic portion  120  of the strap  100  is constructed of a material having minimal longitudinal elongation capability along the length of the strap  100 , though some very slight stretching might occur. In some embodiments the inelastic portion  120  of said strap  100  is constructed of polyester webbing. In other embodiments the inelastic portion  120  of said strap  100  is constructed of nylon webbing. Other materials having the described properties may also be used. The proximate end  124  of the inelastic portion  120  of the strap  100  engages with the ratchet mechanism  200 , as described below. The distal end  126  of the inelastic portion  120  of the strap  100  engages with the elastic portion  110  of the strap  100 , as described below. 
     The elastic portion  110  of the strap  100  has a length, a width, a proximate end  114 , a distal end  116 , an unstretched state, and a stretched state. The elastic portion  110  of the strap  100  is located at the distal end  106  of the strap  100  and its length comprises the lesser portion of the overall length of the strap  100 . In the preferred embodiments the length of the elastic portion  110  of the strap  100  comprises at no more than ten percent of the overall length of the strap  100 . The length of the elastic portion  110  of the strap  100  is capable of being lengthened while under tension to between one hundred twenty-five percent of its length to two hundred percent of its length in its unstretched state. In preferred embodiments the length of the elastic portion  110  of the strap  100  is capable of being lengthened while under tension to about one hundred fifty percent of its length in its unstretched state. The elastic portion  110  of the strap  100  is constructed of a material having elastomeric properties such that the elastic portion  110  of the strap  100  is capable of being stretched longitudinally along the length of the strap  100  when under tension, thereby achieving its stretched state. When said tension is removed the elastic portion  110  of the strap  100  is capable of reverting to its unstretched state. In some embodiment the elastic portion  110  of the strap  100  is constructed of natural rubber. In other embodiments the elastic portion  110  of the strap  100  is constructed of ethylene propylene diene monomer (EPDM). The elastic portion  110  of the strap  100  may be configured as braided elastic webbing or as a woven elastic webbing. Other materials having the described properties may also be used. 
     The proximate end  114  of the elastic portion  110  of the strap  100  is attached to the distal end  126  of the inelastic portion  120  of the strap  100 . This may be achieved through the use of a mechanical fastener  130 . This may be one or more rivets, or stitching, or any other means known in the art for mechanically joining the two portions of the strap  100 . Alternatively, the proximate end  114  of the elastic portion  110  of the strap  100  may be attached to the distal end  126  of the inelastic portion  120  of the strap  100  by an adhesive. This may be created by a heat weld, or by the application of glue, or any other adhesive means. A combination of a mechanical fastener  130  and an adhesive may also be used to attach the proximate end  114  of the elastic portion  110  of the strap  100  to the distal end  126  of the inelastic portion  120  of the strap  100 . 
     In an alternative embodiment, the strap  100  contains a second inelastic portion  140 . See  FIG. 1B . The second inelastic portion  140  of the strap  100  has a length, a width, a proximate end  144 , and a distal end  146 . The second inelastic portion  140  of the strap  100  is located at the distal end  106  of the strap  100  and its length is between fifty percent and two hundred percent of the length of the elastic portion  110  of the strap  100 . In the preferred embodiments the length of the second inelastic portion  140  of the strap  100  is less than the length of the elastic portion  110  of the strap  100 . The width of the second inelastic portion  140  of the strap  100  is substantially the same as the width of the inelastic portion  120  of the strap  100 . The second inelastic portion  140  of the strap  100  is constructed of the same material as the inelastic portion  120  of the strap. The proximate end  144  of the second inelastic portion  140  of the strap  100  engages with the distal end  116  of the elastic portion  110  of the strap  100  by the same means as the distal end of the inelastic portion  120  of the strap  100  engages with the proximate end  114  of the elastic portion  110  of the strap  100 , as described above. 
     The ratchet mechanism  200  is any ratchet mechanism known in the art which is suitable for engaging, retracting, retaining, and releasing the strap  100 . Typically, the ratchet mechanism  200  will have a drum  210 , a take-up handle  220 , gearing, and a release latch  230 . The drum  210  is capable of being rotated in a first direction by operation of said take-up handle  220  and prevented from counter-rotating by the gearing. The drum  210  is capable of being rotated in a second direction opposite the first direction by operation of the release latch  230 , which disengages the gearing. The proximate end  124  of the inelastic portion  120  of the strap  100  is wrapped around the drum  210  when the drum  210  is rotated in the first direction. As more of the proximate end  124  of the inelastic portion  120  of the strap  100  is wrapped around the drum  210 , the shorter the total effective length is of the strap  100 . When the release latch  230  is used to disengage the gearing, a force pulling on the strap  100  will cause the drum  210  to rotate in the second direction resulting in the strap  100  unwinding from the drum  210 , causing the effective length of the strap  100  to increase. The ratchet mechanism  200  is thus seen to be utilized to cause the strap  100  to be drawn taut over a load and to loosen the strap  100  from a load, as desired. 
     The engagement member  300  is any mechanism known in the art which is capable of being attached to the distal end  116  of the elastic portion  110  of the strap  100  and is suitable for engaging with an object  10 . Typically, the engagement member  300  is a hook. This can include flat hooks, snap hooks, wire hooks, grab hooks, s-hooks, and other types of hooks. It can also include buckles, chains, and other grabbing devices. The engagement member  300  may be attached to the distal end  116  of the elastic portion  110  of the strap  100  by any suitable means. In one embodiment the engagement member  300  comprises a slot at one end, with the slot being just slightly wider than the width of the distal end  116  of the elastic portion  110  of the strap  100  so that the distal end  116  of the elastic portion  110  of the strap  100  can be inserted into and through the slot and folded back onto itself, and then secured by a mechanical fastener  130 , an adhesive, or both. Other means for attaching the engagement member  300  to the distal end  116  of the elastic portion  110  of the strap  100  known in the art may also be used. 
     In the embodiments where a second inelastic portion  140  of the strap  100  is used, the engagement member  300  is attached to the distal end  146  of the second inelastic portion  140  of the strap  100 , by the same means as the engagement member  300  is attached to the distal end  116  of the elastic portion  110  of the strap  100  where no second inelastic portion  140  of the strap  100  is used. 
     Where an anchor strap  150  and a second engagement member  310  are used, the anchor strap  150  is constructed of the same type of material as the inelastic portion  120  of the strap  100 , and the second engagement member  310  may be configured substantially identically to the first engagement member  300 . The anchor strap  150  has a length, a proximate end  154 , and a distal end  156 . The length of the anchor strap  150  is substantially less than the overall length of the strap  100 . In some embodiments the length of the anchor strap  150  is less than ten percent of the overall length of the strap  100 . The anchor strap  150  is attached at its proximate end  154  to the ratchet mechanism  200  by any suitable means. In one embodiment the ratchet mechanism  200  comprises a slot at one end, with the slot being just slightly wider than the width of the proximate end  154  of the anchor strap  150  so that the proximate end  154  of the anchor strap  150  can be inserted into and through the slot and folded back onto itself, and then secured by a mechanical fastener  130 , an adhesive, or both. Other means for attaching the proximate end  154  of the anchor strap  150  to the ratchet mechanism  200  known in the art may also be used. The second engagement member  310  is attached to the distal end  156  of the anchor strap  150  by any suitable means. In one embodiment the second engagement member  310  is attached to the distal end  156  of the anchor strap  150  by the same means as the first engagement member  300  is attached to the distal end  116  of the elastic portion  110  of the strap  100 , as described above. Other means for attaching the distal end  156  of the anchor strap  150  to the second engagement member  310  known in the art may also be used. 
     In yet another embodiment of the present invention where an anchor strap  150  and a second engagement member  310  are used, the tie down device  1  includes a retention strap  400 , see  FIG. 1B . The retention strap  400  is used to retain the proximate end  104  of the strap  100  that extends from the ratchet mechanism  200 . In the preferred embodiments the retention strap  400  has affixed to its surfaces hook and loop fasteners  410  such as Velcro™, allowing the retention strap  400  to be looped and secured to itself. So configured, the proximate end  104  of the strap  100  is folded onto itself and the retention strap  400  is wrapped around the folded proximate end  104  of the strap  100  and secured thereto. The retention strap  400  is preferably constructed of the same material as the elastic portion  110  of the strap  100 , such that it can be pulled taut around the folded proximate end  104  of the strap  100 . It may be made of other materials as well. In some embodiments the end of the retention strap may be secured to the anchor strap  150  as shown in  FIG. 1B . The retention strap  400  may be secured using the same means as used to secure the distal end  126  of the inelastic portion  120  of the strap  100  to the proximate end  114  of the elastic portion  110  of the strap  100 . Use of a retention strap  400  allows for the free proximate end  104  of the strap  100  to be kept in good order so that it does not flap about, for example, if the tie down device  1  is being used to secure a load to a moving vehicle. It can also be used to secure the entirety of the strap  100  in good order for storage purposes. 
     Modifications and variations can be made to the disclosed embodiments of the present invention without departing from the subject or spirit of the invention.