Abstract:
The body of the shock absorber is made of lightweight flexible resilient tubular polymer material which will not cause injury when struck by it. The body has a stop in each end and two compression springs within the tubular body between the stops. Tension cables are attached to the compression springs and do not pneumatically engage within the tubular polymer body and extend out of the body and respectively carry a snap hook for attachment to a dog collar and a ring for attachment to a dog leash. Pull on the tension members causes compression of the springs to reduce shock-loading on the dog walker. After the springs are pulled solid, the resiliency of the body continues to absorb shock.

Description:
CROSS REFERENCE 
   This application relies on my earlier filed applications, Ser. No. 60/650,387, filed Feb. 4, 2005, Ser. No. 11/097,845, filed Apr. 4, 2005, and Ser. No. 11/541,595, filed Oct. 2, 2006, for priority, the entire disclosures of which are incorporated herein by this reference. 
   BACKGROUND OF THE INVENTION 
   In urban environments, dogs are required to be leashed when they are outside their own home fence limits. Dogs usually wear a collar at all times. These collars carry the dog license and sometimes the dog&#39;s separate identification. The collar also has an eye thereon which can be engaged by a leash. Dogs are often taken for a walk while controlled by a leash. 
   The leash is carried in the walker&#39;s hands and is snapped to the eye in the dog&#39;s collar. Sometimes the dog is large and the dog walker is small. When a dog becomes excited, for example, chasing a squirrel, uncomfortable and sometimes damaging shock can be transferred through the leash to the dog walker. In order to protect the dog walker&#39;s arm against damage, a shock absorber which can be installed between the leash and the dog collar is desirable. 
   SUMMARY OF THE INVENTION 
   In order to aid in the understanding of this invention, it can be stated in essentially summary form that it is directed to a shock absorber for attachment to a dog leash. The shock absorber is comprised of a flexible tubular body having a spring therein. The spring is preferably a spiral compression spring with the body configured so that spring failure is in the safe mode. One end of the body carries a snap hook for engaging in the eye of the dog collar and the other end has a ring for engagement by the snap hook on a conventional leash so that the shock absorber can be installed between the collar and the leash. 
   It is, thus, a purpose and advantage of this invention to provide a shock absorber for a dog leash wherein the shock absorber is positioned between the dog collar and leash so that it reduces the shocks transmitted by the dog to the dog walker. 
   It is another purpose and advantage of this invention to provide a shock absorber constructed with a body of flexible tube and with at least one compression spring therein. The compression spring is mounted in the body in a manner that, if the spring fails, the shock absorber will not come apart. 
   It is another purpose and advantage of this invention to provide a shock absorber which is small in size and light in weight so it can be easily used, and which can be readily manufactured so as to be widely available. 
   It is another purpose and advantage of this invention to provide a shock absorber which has a snap hook on one end configured to snap into the eye in a dog collar and which has a loop on the other end configured to be engaged by the snap hook on a dog leash so that it can be readily inserted between existing collars and dog leashes. 
   Other purposes and advantages of this invention will become apparent from a study of the following portion of the specification and the following drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side-elevational view of the shock absorber for a dog leash in accordance with this invention utilized between a dog and a dog walker. 
       FIG. 2  is a side-elevational view of the shock absorber in the unstressed condition which, in this case, has a transparent body so that the interior structure can be seen. 
       FIG. 3  is a longitudinal section thereof, with parts broken away and parts taken in section. 
       FIG. 4  is a view similar to  FIG. 2 , showing the shock absorber in the stressed, shock-absorbing position. 
       FIG. 5  is an enlarged transverse section taken generally along the line  5 - 5  of  FIG. 2 . 
       FIG. 6  is an enlarged detail which is a sectional view through the cap attached to the end of the cable. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The shock absorber of this invention is particularly suitable for dogs when on a leash, but is also suitable for other animals in other circumstances. The shock absorber is generally indicated at  10  in  FIGS. 1 ,  2 ,  3 , and  4 . The body  12  of the shock absorber is a tubular structure and is made of synthetic polymer composition material. In  FIG. 2 , the body is shown as being made of clear synthetic polymer composition material so that the internal structure is visible, but in commercial production is preferably of opaque material. The material of the body is flexible and resilient. For the purposes of this invention, flexible is defined as having a modulus of elasticity E not greater than about 2×10 3 . Stiffness greater than that value is not desired or helpful. The modulus of elasticity E is the ratio of the increment of unit stress to increment of deformation within the elastic limit. The material of the body is sufficiently resilient so that its elasticity is no more than 2×10 3  in the foot pound second system. The strength and resiliency is such that it can be stretched to 150% of its unstressed length. It is a cylindrical tube of substantially uniform wall thickness and substantially uniform diameter such as is achieved by extrusion. The synthetic polymer composition material of the body is sufficiently flexible and resilient so that it does not hurt when the user is inadvertently struck by the tubular body. In addition, it is resilient and of low enough spring constant so that it stretches in normal use to additionally absorb shock. 
   Tubular stops  14  and  16  are secured in the ends of the body  12 . The tubular stops are each also circular cylindrical tubes of synthetic polymer composition material, preferably the same material as the body. The tubular stops are secured in place in the ends of the body, such as by adhesive or thermal welding. The left end of the shock absorber  10  is considered to be the snap end. 
   Exteriorly of the body is a snap hook  18  sized to conveniently snap onto the eye in a dog collar. The snap hook  18  has a hook  20 . Finger  22  is pivotally mounted on the body of the hook and is spring-loaded to stop against the hook in the closed position shown in  FIGS. 2 and 3 . Thus, the snap hook can be snapped onto a ring, such as one on a dog&#39;s collar. Swivel connector  24  is mounted on a swivel pin on the end of the snap hook away from the hook. Swivel connector  24  has an opening in its right end which receives connector cap  26 . 
   The connector cap  26  is similar to the connector cap  28  shown in  FIG. 6 . The connector cap  28  has a shank  30  and a head  32 . The head is much smaller than the inside of the body so that it has no pneumatic effect. The shank has a central opening  34  which is sized to receive the end of cable  36 . At least the shank portion of the connector cap  28  is made of malleable material so that it may be crimped or swaged down onto the cable to secure the cap on the cable. Depression  38  is seen in  FIG. 6  as representing this malleable distortion which secures the connector cap onto the cable. As seen in  FIGS. 2 and 3 , the connector cap  26  is secured to the left end of the cable, and the connector cap  28  is secured to the right end of the cable. Compression spring  40  is positioned between connector cap  28  and stop  14 . Without sealing therein, the connector cable  36  extends out through clearance hole  37  in the stop  14  where it is engaged in the swivel connector  24 . 
   The cable  36  extends out through the opening in the stop  14  without sealing. The cap  28  is spaced from the interior wall of the tube of body  12  so that there is no significant piston action between the cap  28  and the body. In addition, the fact that the cable  36  is smaller than the opening through the stop  14 , there is no pneumatic result. There is no significant increase or decrease of pressure within the tube when the springs are stressed, so there is no pneumatic action. In fact, under tension the cables  36  and  50  are pulled out of the body with the result there is less material within the body so that air would flow in through the openings in the stops, rather than build up pressure. There is no piston action and there is no seal action. Thus, tension on cable  36  causes compression of spring  40 . 
   The ring end of the shock absorber is similar to the snap end. It is called the ring end because it carries an external ring  42  sized to be conveniently engaged by the snap hook on the end of a dog leash. Dog leash  44 , shown in  FIG. 1 , is held by a dog walker  46  who controls dog  48 . A flexible tension member in the form of cable  50  is engaged on the ring  42  and extends inward through clearance hole  43  in the tubular stop  16 , without sealing, see  FIGS. 2 ,  3  and  4 , and through compression spring  52 . The ring  42  is attached to the end of cable  50  by means of a connector cap  54 , which is the same as connector cap  26 . The connector cap  54  is crimped onto the outer end of cable  50 . The cable  50  extends through the central opening in stop  60  and through compression spring  52  into the connector cap  56  crimped onto the left end of the cable  50 . Both of the springs  40  and  52  are wound so that the end engaged by the connector caps  28  and  56 , respectively, are smaller than the principal body of the springs. 
   The body of spring  52  is the of the same diameter as the body of spring  40 . Only the ends adjacent the connector caps need be reduced, and they are only reduced in order to provide a secure contact between the connector cap and the compression spring. The spring  52  has a smaller diameter wire and thus has a lower spring constant (amount of deflection per unit force) as compared to the spring  40 , which has a larger diameter and thus less deflection per unit force. The unstressed length of the spring  52  is about twice the unstressed length of the spring  40 . 
   When axial tension is applied between the hook  18  and ring  42 , the spring  52  first compresses and becomes solid, while the heavier spring  40  is only half compressed. This means progressive increase of force with the force per unit of spring deflection increasing in rate as the longer spring  52  becomes solid. This extends the range over which the shock absorber  10  is effective. Another important factor in shock absorption is that the body  12  is made of resilient polymer composition material. It also stretches up to 50% under tension to additionally absorb shock. After the two springs are solid, the body continues to stretch under additional load. 
     FIG. 1  illustrates the use of the shock absorber  10 . The dog leash  44  is connected by a snap hook to ring  42 . The snap hook  18  of the shock absorber is connected to the dog collar. The dog walker now has the shock absorber  10  between himself and the dog  48 . Should the dog give a jerk, the springs  40  and  52  compress. In addition, the resilient body  12  stretches under tensile load.  FIG. 4  shows the pulling of the cables  36  and  50  out of the body, with consequent compression of the springs  40  and  52 . In this way, the dog walker  46  is protected from sudden shocks. 
   The substantial convenience of creating the body of the shock absorber out of flexible material is that, with its flexure it will not hurt the dog or the dog walker should it be moved suddenly and strike one or the other. Furthermore, use of polymer material permits the shock absorber to be resilient, strong and lightweight so that it absorbs shock and is less of a burden to carry around. 
   This invention has been described in its presently preferred embodiment, and it is clear that it is susceptible to numerous modifications, modes and embodiments within the ability of those skilled in the art and without the exercise of the inventive faculty. Accordingly the scope of this invention is defined by the scope of the following claims.