Abstract:
A leash booster adapter is descripted which is attach to each end of a section of pet leash, and comprises an elastic member between shorter than the pet leash section to which it attached. In use, the device applies progressive resistance to the pet proportional to the stretching force provided by the pet pulling on the leash: the harder the pet pulls, the more resistance is felt. Rather that a hard jerk felt by the pet when it pulls, a gentle resistance is first felt, increasing in force as the pet pulls harder.

Description:
This application claims priority from provisional patent application No. 62/021,852 filed Jul. 8, 2014, which is incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to pet products, and more particularly to leashes and restraints. 
     BACKGROUND OF THE INVENTION 
     Walking a pet on a retractable leash can be problematic with pets that pull or lunge. Similarly, a pet tied to a run may leap against the restraint. Because the restraint is inelastic, the pet can be subject to a jerking force on the pet&#39;s neck. This jerking can result in neck injuries to the pet if on a collar, and other injuries even if on a harness, such as muscle tears. A large dog lunging can put repeated strain or shock on the pet owner&#39;s arm, wrist or shoulder. 
     What is needed is a device that progressively encourages the pet not to strain against the leash or restraint, in a safe and less injury prone manner than just a leash. By progressive, what is meant is that the harder the pet may pull, the more the pet should be encouraged not to pull. 
     BRIEF SUMMARY 
     In one embodiment according to the principles of the present invention, the leash booster adapter comprises an assemble of an elastic member, a means of connecting each end of the elastic member to two attachment points on a leash, respectively. In a preferred embodiment, the elastic member is from 3 to 14 inches long, and sized to have a spring constant appropriate for the size and weight of the pet on which the leash booster adapter is to be used. Using means such as, for example, a bibb washer through which a loop of leash is pulled and secured over the washer with a cow hitch, two point attachment points may be installed on a leash, such as a retractable member leash. 
     The elastic member may, in yet another embodiment, be fitted with grommets on each end to facilitate attachment to the attachment points. In yet another embodiment, the grommets may be installed over a d-ring adapter with the wire end protruding from the end of the member and secured with a rivet, or a nut and bolt. 
     Instead of a bibb washer, other materials may be used latex tubing such as surgical tubing. Other elastic materials may be used, such as rubber, shock or bungee member or even a spring It is preferable that the two attachment points be farther apart on the leash than the combined length of the elastic member and the means to attach to the leash, and no more than twice the length of the elastic member. 
     Connecting means may comprise, in exemplary embodiments, the elastic member may be made from latex tubing such as surgical tubing. Other elastic materials may be used, such as rubber, shock or bungee member or even a spring. 
     Other than a bibb washer, other embodiments may comprise a metal washer, plastic washer, faucet washer, rubber washer, metal ring, quick link with a spring closure, a quick link with a threaded closure and a shackle for the attachment points. 
     In yet another embodiment, the present invention comprises a method of adapting a pet leash to provide gentle and progressive restraint against pet pulling by connecting with connecting means a length of elastic material between two means of attachment on a pet leash. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will be better understood by reading the following detailed description, taken together with the drawings wherein: 
         FIG. 1  is a drawing of one embodiment of a leash booster adapter. 
         FIG. 2 . is a drawing of a d-ring hanger used in one embodiment of a leash booster adapter. 
         FIG. 3  is a drawing of a leash booster adapter assembled onto an exemplary retractable leash. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features and advantages of the invention will become apparent from the description, the drawings, and the claims. 
     According to the principles of the present invention, a length of elastic material is connected at one end to a first point on a leash, and at the other end connected to a second point on the leash father away from the first point than the length of the elastic member, this making a “leash loop” (shown in  FIG. 3  as leash loop  70 ) around the elastic member. The size of the loop establishes the maximum extension of the elastic member when the pet attempts to strain on the leash, and provides a failsafe against the failure of the elastic member. 
     In use, when the pet is connected to the leash and begins to strain on the leash, the elastic member is stretched (allowed to do so by the loop of leash) and gently pulls back on the pet. If the pet pulls harder, the elastic member is stretched further and thus applies greater restraining force, proportional to how hard the pet pulls. If the pet applies enough force that it stretches the elastic member to the length of the leash loop, the strain is taken up strongly by the leash. 
     In use, the elastic member provides a spring or elastic tension against the pet pulling, increasing tension as the pet pulls harder, the tension being approximately calculated by the spring constant of the elastic member chosen according to the formula F=−kx, where F is the force applied by the elastic member, k=the spring constant of the elastic member, and x being the length of stretching applied to the elastic member by the force applied. 
     Referring to  FIG. 1 , one exemplary embodiment  10  of a leash booster adapter according to the principles of the present invention is shown. There is a central elastic member  15  made from, for example, latex tubing such as surgical tubing. Other elastic materials may be used, such as rubber, shock or bungee member or even a spring, chosen to give the desired coefficient of elasticity to restrain a pet of given size and for weight. The elastic member should be chosen to have appropriate strength, durability and elasticity when stretched for the size and weight of the pet with which it will be used: for a smaller animal of 8 to 20 pounds, latex tubing from ¼ inch to a half inch has been found appropriate; for a larger, heavier pets, larger size tubing should be chosen. If using another material for the elastic member  15  it should be chosen to give the appropriate pull on a pet of given strength and size. A length for the elastic member of three to fourteen inches has been found most advantageous. 
     While it is possible to tie the elastic member to the leash at two points, other means of connection have been found more beneficial, secure and easily removable. For example, metal rings (not shown) may be tied to each end of the elastic member  15 , and then the leash either tied to the metal rings or attached to the leash with snap hooks or clips. This too suffers from being more difficult to remove and less secure than the referred embodiments described below. 
     In an embodiment using latex tubing as the elastic member  15 , it has been found advantageous to install grommets  20 A and  20 B at either end of the elastic member  15  as part of the attachment means. While the grommets  20 A,  20 B will suffice for attachment of the elastic member  15 , it has been found to be advantageous to secure D-ring hangers  30   a  and  30 B within grommets  20 A and  20 B as part of the attachment means attachment points. 
     With reference to  FIG. 2 , one exemplary d-ring hanger is shown. It comprises a stiff metal wire  30 B for attachment, a flat metal plate  31 B bent at one end around the wire  30 B to form a hinge  32 B around the wire  30 B, and a hole  33 B through which a rivet, such as a pop rivet or a nut and bolt to secure the assembly through grommet  20 B. Both connection wires  30 A and  30 B may be so secured with rivets  25 A,  25 B respectively. The d-ring hangers should be installed so that the wire loop protrudes beyond the ends of the elastic member. 
     A myriad of other connecting solutions using off-the-shelf hardware and custom hardware will be apparent to those skilled in the art. 
     To make the leash booster adapter more readily removable from the leash, the embodiment shown in  FIG. 1  uses as part of the connecting means double ended carabiners  35 A and  35 B to connect the elastic member  15  to the leash  40 A and  40 B. A single carabiner could also be used. The carabiners  35 A  35 B have spring closures at each end ( 36 A and  37 A, and  36 B and  37 B, respectively) for easy attachment detachment. Many other connecting solutions from standard hardware will be apparent to those skilled in the art, such as, for example, metal S hooks that my be bent to close them, shackles or split links, snap hooks, quick links (both threaded and spring opening) and the like. 
     The carabiner strength rating will change as will the latex tubing elongation and tensile strength rating as the device is made for use with smaller or larger dogs. 
     The purpose served by the connecting means, whatever is used, is to connect the elastic member  15  to the leash attachment means, which in this embodiment comprises washers  45 A and  45 B which have holes in the center of them. At each desired point of attachment to the leash, a small loop is formed in the leash and the loops are pushed through each of washers  45 A and  45 B respectively, Each loop is brought around the bodies of washers  45 A  45 B respectively to form a cow hitch knot. A simple hard rubber bibb washer has been found to be particularly suitable. Other forms of leash attachment means may be used beneficially, such as metal rings. 
       FIG. 3  shows an exemplary embodiment  50  of the present invention assembled to a retractable leash  55 . The leash member (comprising segments  40 B,  70  and  40 A) is attached at two points  40 A and  40   b  with cow hitches to the leash booster adapter  10 . This forms a leash loop  70 . The leash loop  70  should be longer, ideally from 1.25 to 2 times the length of the leash booster adapter  10 , depending upon the strength and elasticity of the elastic member  15 . The leash loop  70  length should permit the elastic member  15  to stretch when the leash booster adapter  10  is under tension, but short enough to limit the stretching to prevent the elastic member  15  from over-stretching or breaking if the pet pulls too hard. 
     In a preferred embodiment, the leash booster adapter is attached at one end approximately six to fifteen inches from the pet&#39;s collar, and at the second end 20 inches further up the leash. The leash booster adapter  10  thus becomes the “direct line of comfort” while the original leash remains intact for uninterrupted safety. 
     The double caribiners in this embodiment  35 A and  35 B are hooked at one end through washers  45 A and  45 B respectively 
     The invention has been described in terms of particular embodiments. Other embodiments are within the scope of the following claims. For example, the steps of the invention can be performed in a different order and still achieve desirable results. While the present invention has been described in terms of a reel-type retractable member leash, other leash types may be used, with modifications to the attachment means readily apparent to those skilled in the art. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims.