Abstract:
A retractable tow strap apparatus includes a housing containing a spool operably connected to a crank on the exterior of the housing. A tow strap is wound around the spool, the ends of the strap extending through a pair of apertures on opposite sides of the housing. Unwinding the strap from the spool through the apertures rotates the spool in a first direction. The strap is retrieved onto the spool by rotating the spool in a second direction using the crank. Springs within the housing apply a braking force on the portion of the strap that is on the spool, whereby slack in the strap and resultant tangling may be minimized as the strap is wound and unwound from the spool. The strap is formed of a unitary webbing element that extends through the spool, thereby minimizing the application of tension forces directly to the spool during a towing operation.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Not applicable. 
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND 
     The present disclosure relates generally to a tow strap for towing a vehicle, and in particular, to a retractable tow strap for towing a vehicle. 
     Tow straps can be used to tow a wide variety of vehicles. Tow straps are often chosen because they offer a significant weight savings over other towing connectors, such as tow chains or tow bars. However, a loose tow strap can be difficult to store, especially when a relatively longer length tow strap is used. Most vehicles have limited storage space and motorists must weigh the use of that space for many purposes. While many motorists choose to use at least some of the available storage space for automobile emergency equipment, the ability to containerize the equipment or size of the container itself often plays a role in the decision, with preference being given to effective equipment that fits in smaller containers. 
     Self-retracting tow straps are known, but self-retracting mechanisms can be unreliable, rendering the tow strap inoperable when the strap is most needed. Tow straps that are not containerized suffer none of the malfunctions of the self-retracting straps, but are bulky and difficult to store efficiently. In an emergency situation, operability is critical; however, emergency situations tend to occur rarely. Accordingly, most tow straps will spend most of their time in storage somewhere in a motor vehicle. Thus, it is important that a tow strap store easily, but it is critical that the strap work when it is needed. Accordingly, it would be beneficial to provide a retractable tow strap apparatus that can overcome the aforementioned problems. 
     SUMMARY 
     The various embodiments of the present tow strap apparatus have several features, no single one of which is solely responsible for their desirable attributes. Without limiting the scope of the present embodiments, their more prominent features now will be discussed briefly. After considering this discussion, and particularly after reading the section entitled “Detailed Description,” one will understand how the features of the present embodiments provide advantages over known tow strap devices, including reliable operation, convenient storage, and ease of use in both deploying the strap and recovering it for storage. 
     In accordance with an aspect of the present disclosure, a retractable tow strap apparatus or device includes a protective housing having first and second diametrically-opposed openings or slots, and containing a manually-rotatable spool on which is wound a tow strap having first and second ends that extend from the first and second housing slots, respectively. One end of the spool extends to the exterior of the housing, where it is fixed to a hand crank. The tow strap extends through the central portion of the spool and is fixed to it, so that unwinding the strap from the spool rotates the spool, and thus the crank, in a first direction, while rotating the spool in a second direction by means of the crank rewinds the strap onto the spool. The strap has a fully wound or retracted position on the spool in which each of the first and second ends extends a short distance from its respective slot, and a fully unwound or extended position in which approximately one-half the total length of the tow strap extends from each of the first and second slots. Thus, in its extended position, substantially the whole length of the strap is unwound from the spool and deployed from the housing. 
     The tow strap is deployed from its retracted position to its extended position by pulling on the first and second ends of the strap, thereby unwinding the strap and rotating the spool and the crank in the first direction. The strap is withdrawn from its extended position to its retracted position by manually turning the crank in the second direction, thereby rotating the spool in the second direction to rewind the strap onto the spool. Preferably and advantageously, the housing contains one or more resilient braking members that frictionally engage the strap with a braking force as the latter unwinds from and winds onto the spool. This braking force provides a slight tensioning to the strap as it is paid out from the spool, thereby preventing, or at least substantially limiting, inadvertent unwinding due to the weight of the towing hooks that are typically attached to each end of the strap. This tensioning also minimizes backlash and tangling that could result from excessively rapid recovery of the strap onto the spool. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a back side elevation view of tow strap apparatus in accordance with an embodiment of this disclosure, showing the tow strap in a retracted position; 
         FIG. 2  is a front side elevation view of the tow strap apparatus of  FIG. 1 ; 
         FIG. 3  is a top plan view of the tow strap apparatus if  FIG. 1 ; 
         FIG. 4  is a bottom plan view of the housing of the tow strap apparatus of  FIG. 1 ; 
         FIG. 5  is an exploded perspective view of the tow strap apparatus of  FIG. 1 , with the strap and carrying handle removed for clarity; 
         FIG. 6  is a cross-sectional view of the tow strap apparatus of  FIG. 1 , showing the strap in an extended position; 
         FIG. 7  is a view similar to  FIG. 6 , but with the tow strap in a retracted position; 
         FIG. 8  is a detailed view of a spool used in an embodiment of this disclosure; 
         FIG. 9  is a view of the spool shown in  FIG. 8 , rotated by 90 degrees; 
         FIG. 10  is a view of the spool shown in  FIGS. 8 and 9 , taken from the right side of  FIGS. 8 and 9 ; and 
         FIG. 11  is an enlarged detailed view of the spool shown in  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below in connection with the appended drawings is intended as a description of embodiments of a tow strap apparatus provided in accordance with aspects of the present disclosure, and it is not intended to represent the only forms in which the present apparatus may be constructed or used. The description sets forth the features and the steps for using the tow strap apparatus of the present disclosure in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and structures may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the disclosure. As denoted elsewhere herein, like element numbers are intended to indicate like or similar elements or features. 
     Referring first to  FIGS. 1-5 , an embodiment of a tow strap apparatus  10  in accordance with this disclosure is shown. The apparatus  10  includes a housing  12  that may advantageously comprise a first half  12   a  defining a first side wall  14  ( FIG. 1 ) and a second half  12   b  defining a second side wall  16  ( FIG. 2 ). The housing halves  12   a ,  12   b  are secured together at their peripheries by fastening elements, such as screws  18 , for ease of construction and repair. Other fastening means, such as thermo-welding, sonic welding, adhesives, or snap fasteners, may be used. The house  12  may be made from a rigid and durable material, such as a metal or a molded polymeric material. Although the house  12  is shown with a configuration defining an elliptical perimeter, this configuration is exemplary only, and other configurations, such as circular, square, or polygonal may be used. 
     The housing  12  defines a peripheral wall  20  having a top area to which a carrying handle  22  is fixed. The peripheral wall  20  is further configured with first and second opposed end areas, each of which defines an elongated aperture or slot  26 . As will be further described below, the opposed slots  26  accommodate a tow strap  28 . As shown in  FIG. 4 , the peripheral wall  20  has a bottom area that may advantageously be provided with a plurality of drainage holes  29  that allow the drainage of moisture from the interior of the housing  12  that may accumulate therein from water on the strap  28 . 
     As shown in  FIG. 2 , the second side wall  16  of the second housing half  12   b  defines a substantially circular recess  30  that accommodates a hand crank  32 . Preferably, the recess  30  is deep enough so that the crank  32  is either flush with, or slightly recessed from, the portion of the second side wall  16  surrounding the recess  30 . The crank  32  is shown with four gripping lobes  34  radiating from a central hub  36 , but the lobes  34  may be from two to five in number, with the number and configuration of the lobes  34  depending on design and operational considerations. As will be discussed below, the hub  36  is fixed to one end of a spool  38  that extends through an aperture  40  (see, e.g.  FIG. 5 ) in the second side wall  16 . 
     The tow strap  28  comprises a single, unitary length of webbing, preferably of a high tensile-strength, stretch-resistant polymer such as nylon or polyester, having first and second looped ends  42 , each of which is secured, by conventional means, to a tow strap attachment implement, such as a tow hook  44 . The total length of the strap  28  may be from about 5 feet (1.5 m) to about 20 feet (6 m), or even more, depending on the application. The strap  28  should be strong enough to tow a vehicle. Each of the looped ends  42  extends from one of the slots  26 , the latter being narrow enough to prohibit withdrawal of the looped ends  42  into the interior of the housing  12 . The slots  26 , through which the tow strap  28  passes, may advantageously have rounded edges to minimize frictional wear on the tow strap  28  as it passes through the slots  26  during extension and retraction, as will be described below. 
     Referring now to  FIGS. 5-11 , first and second circular walls or flanges  50 ,  52  are attached to first and second ends, respectively, of the spool  38  so as to be rotatable with the spool  38 . A nub  54  is fixed to the side of the second flange  52  opposite the spool  38  and is disposed coaxially with the spool  38 . The nub  54  extends through the aperture  40  in the second side wall  16 , and it is configured to fit into a socket  55  on the hack side of the huh  36  of the crank  32 . The nub  54  of the spool  38  may advantageously be provided with a threaded aperture  59  ( FIG. 8 ), or, alternatively, a through-bore (not shown) to accommodate a threaded fastener  57 , such as a screw (a self-tapping screw, if a through-bore is provided), to secure the crank  32  to the nub  54 . The nub  54  and the socket  55  are preferably non-circular in shape, to minimize relative rotational movement between the crank  32  and the spool  38 , so that the crank  32  and the spool  38  are rotatable as a unit. Advantageously, the aperture  40  in the second side wall  16  of the housing  12  may have an inwardly-extending peripheral rim  56 , and the nub  54  may have a maximum dimension just slightly smaller than the diameter of the aperture  40 , so that the peripheral rim  56  of the aperture  40  provides a bearing surface for the nub  54 , thereby minimizing slackness or “play” between the nub  54  and the aperture  40 . The end of the spool  38  to which the first flange  50  is attached advantageously extends through a central flange aperture  58  and is configured to seat rotatably in a socket (not shown) on the inner surface of the first side wall  14  of the housing  12 . 
     The spool  38  is split into two semi-cylindrical axial segments by a diametric slot  60  configured for the passage of the strap  28  through it. The spool  38  is preferably situated within the housing  12  so that the spool  38  has rotational positions in which the slot  60  of the spool  38  may be in substantial alignment with the slots  26  of the housing  12 . Thus, the strap  28  passes through one of the housing slots  26 , through the shaft slot  60 , and then through the opposite housing slot  26 . This arrangement allows the unitary strap  28  to be wound or coiled on the spool  38  in a retracted position or state, such that when the strap  28  is deployed to its extended position or state by unwinding it from the spool  38 , the spool  38  is rotated in a first direction, along with the crank  32  that is attached to it, as described above. When the spool  38  is rotated in the opposite (second) direction by turning the crank  32  in the second direction, the strap  28  is retrieved through the housing slots  26  and re-wound back onto the spool  38  to its retracted position or state. The length of the spool  38  between the flanges  50 ,  52  is advantageously slightly greater than the width of the strap  28 , so that the strap  28  may stay in alignment with the side slots  26  of the housing  12 . 
     As shown in  FIGS. 6-11 , the outer surface of the spool  38  may advantageously be configured with a plurality of longitudinal ridges  62  spaced around the circumference of the spool  38 , to provide an improved frictional grip between the spool  38  and the initial windings of the strap  28 . Also as shown in these drawing figures, the diametric slot  60  in the spool  38  may advantageously be provided with an array of gripping protuberances or teeth  64  on each side of the spool slot  60 . These protuberances or teeth  64  grip the strap  28 , so that the house  12  cannot easily be moved from its normal position in the approximate center of the strap  28 . Centering of the housing  12  with respect to the length of the strap  28  assures that the strap  28  is consistently wound evenly on the spool  38 , with approximately one-half the length of the strap  28  being consistently available to be extended from, and retrieved by, the spool  38  through each of the housing slots  26 . 
     Referring to  FIGS. 5-7 , a pair of Z-shaped biasing springs  70  is mounted in the interior of the housing  12 , one at the top of the housing, and one at the bottom. As best shown in  FIG. 6 , each of the springs  70  is formed from a strip of spring metal that is bent into a Z-shape, with a first horizontal segment  72  secured to the interior of the housing  12  by means such as mounting tabs  74 , advantageously formed as part of the housing, and a second horizontal segment  76  connected to and spaced from, the first horizontal segment  72  by a diagonal connecting segment  78 . The springs  70  have an uncompressed or unbiased state ( FIG. 6 ) when the strap  28  is unwound from the spool  38  to its fully extended condition (i.e., the spool  38  is empty), and a fully compressed (fully biased) state ( FIG. 7 ) when the strap  28  is fully wound onto the spool  38  in the retracted position of the strap  28  (i.e., the spool  38  is full). 
     In the uncompressed state of the springs  70 , the second horizontal segment  76  of each spring  70  seats against the empty spool  38 . As the spool  38  is rotated, as described below, to retrieve the strap  28  from its extended state onto the spool  38 , the coiling of the strap  28  onto the spool  38  urges the second horizontal segment  76  toward the first horizontal segment  72  of each spring  70 , thereby placing the springs  70  in compression. This compression of the springs  70  creates a frictional braking or biasing force to the portion of the strap  28  that is coiled on the spool  38 , thereby applying a slight tensioning to the strap  28  as it is paid out from the spool  38 . This tensioning substantially limits any inadvertent or undesired unwinding of the strap  28  from the spool  38  due to the weight of the towing hooks  44 , while also minimizing backlash and tangling that could result from excessively rapid recovery of the strap  28  onto the spool  38 . Optionally, a friction-enhancing material or surface treatment (not shown) may be provided on the surfaces of the second horizontal spring segments  76  that engage the strap  28  to increase the amount of braking force applied by the springs  70 . 
       FIGS. 1 ,  2 ,  3 , and  7  show the tow, strap  28  in its fully retracted position, in which, as best shown in  FIG. 7 , the strap  28  is fully coiled or wound onto the spool  38 . The strap  28  may be unwound from the spool  38  by attaching one of the tow hooks  44  to a stationary structure (such as a vehicle to be towed) and attaching the other tow hook  44  to a driven vehicle that is moved away from the stationary structure. Alternatively, a pulling force can be applied to one or both of ends of the strap  28  and/or the tow hooks  44 . The crank  32  may also be turned in the first rotational direction, thereby rotating the spool  38  in the same direction to unwind the strap  28  from the spool  38  under the weight of the tow hooks  44 . As mentioned above, the springs  70  maintain a frictional braking force against the strap  28  as it unwinds to minimize slack in the strap  28 , thereby greatly reducing the possibility of tangles of the strap within the housing  12 . When the tow strap  28  is in its fully extended position or state, as shown in  FIG. 6 , the strap  28  extends approximately equidistantly from both side of the house  12 , which is thus positioned at approximately the center of the extended strap  28 . 
     When the tow strap  28  is in the fully extended position, the tow strap apparatus  10  is configured to transmit substantially all of a tension force applied by a towing vehicle to a towed vehicle through only the tow strap  28  itself, without any tension forces applied to the structure of the housing  12 , and with relatively little tension applied to the spool  38 . This advantageous result is largely the result of the geometry of the spool  38 , in which the diametric slot  60  permits the unitary strap  28  to pass completely through the spool  38 , with the only contact between the strap  28  and the spool  38  being through the gripping protuberances or teeth  64  (which are not configured as substantial load-bearing elements). Thus, when the tow strap  28  is in the fully extended position ( FIG. 6 ), substantially all of the tension force can be transmitted through the tow strap  28  and the tow hooks  44 . Thus, because neither the housing  12  nor the spool  38  is a major load-bearing component, they can be made of lighter, less expensive materials. 
     When the tow hooks  44  are freed from their respective vehicles or the like, the tow strap may be retrieved from its extended position or state ( FIG. 6 ) and returned to its fully retracted position ( FIG. 7 ) by turning the crank  32  in the second direction, which, in turn rotates the spool  38  in the second direction. The strap  28  is then withdrawn into the housing  12  through the housing apertures or slots  26  and re-wound onto the spool  38 . The longitudinal ridges  62  on the spool  38 , as discussed above, enhance the frictional grip between the spool  38  and the strap  28  for the initial windings of the strap  28 . As additional windings of the strap  28  are pulled on to the spool  38 , the flanges  50 ,  52  guide the strap  28  so that it remains centered on the spool  38 . The springs  70  maintain a frictional braking force against the strap  28 , as discussed above, to minimize slack in the strap  28 , thereby substantially reducing the possibility of tangles in the strap  28  within the housing  12 . As the user continues to turn the crank  32 , the strap  28  is progressively wrapped about itself to form a doubly-wound coil. In the fully retracted position ( FIG. 7 ), the tow strap  28  is generally completely wound around the spool  38 , although the looped ends  42  of the tow strap  28  will remain outside the housing  12 . The force of the springs  70  against the strap  28  within the housing  12  helps keep the strap from inadvertent unwinding when the apparatus  10  is stored. 
     The disclosure has been described with reference to various example embodiments. Modifications and variations may suggest themselves upon a reading and understanding of this specification. It is intended to include all such modifications and variations insofar as they come within the scope of the appended claims or the equivalents thereof.