Abstract:
Springs or other elastic connectors used to support a bed within the frame of a trampoline or the like are attached using methods that systematically vary the tension (or the travel distance required to reach limit of elasticity) between adjacent (or sets of adjacent) springs. These spring attachment methods increase the time it takes a given trampoline to absorb a given amount of energy, increasing the shock absorption time and thereby reducing the likelihood of an injury.

Description:
[0001]     This is a continuation of application Ser. No. 10/110,884, filed Apr. 15, 2002, which is the National Stage of International Application No. PCT/US01/25544, filed Aug. 14, 2001, which claims the benefit of Provisional Application No. 60/225,135, filed Aug. 14, 2000, which applications are incorporated herein by reference. 
     
    
     BACKGROUND AND SUMMARY  
       [0002]     The present invention concerns jumping surfaces used with trampolines to protect trampoline users from injury, and to provide new uses for trampolines. In the past, trampolines have been used for a variety of athletic and recreational purposes. However, thousands of injuries have resulted when persons jumping on a trampoline have landed on the rebounding surface while in an awkward or incorrect body position. These “on-bed” injuries, according to some medical studies, represent the majority of trampoline-related emergency room visits. The U.S. Consumer Products Safety Commission (CPSC) reports that in 1999 approximately 110,000 people were treated in emergency rooms for trampoline related injuries. Even though this number is half that of playstructure/swingset injuries, some in the medical community have called for a ban on the sale of backyard trampolines. The CPSC and the AAOS have taken a more responsible and measured approach to problem. Recognizing that other outdoor activities that are more injurious, like bicycling, would fill the void left by backyard trampoline play, these organizations have instead called for safety improvements to help reduce the disturbingly large number of trampoline injuries.  
         [0003]     One approach to reducing trampoline injuries has been to form a wall around the perimeter of a trampoline bed so that when a jumper lands too near the edge, the wall prevents the jumper from falling off. Examples are shown in U.S. Pat. Nos. 5,399,132 and 6,053,845. However, these devices do not directly address injuries that result when users impact the rebounding surface incorrectly or while in an awkward position. A second approach, the use of a harness (worn by the jumper) suspended by elastic cords above the rebounding surface, is an effective way to reduce on-bed, or rebound surface impact injuries. However, such harnesses are designed for safely teaching users advanced acrobatics on high-performance competition trampolines by trained professionals, making them largely inappropriate for low-performance backyard trampolines that are used almost entirely for basic jumping activities and not for advanced acrobatics.  
         [0004]     All things being equal, a bed with less tension is more forgiving when a jumper first contacts its surface, it absorbs the impact more slowly and will thus reduce the severity and quantity of on-bed injuries. Nevertheless injuries suffered during an impact with the rebounding surface are still occurring in large numbers on backyard trampoline beds even though these beds are designed to be less responsive and to have less initial surface tension than gymnastic grade, competition trampoline beds. Reducing bed-impact injuries, especially those that occur on backyard trampolines, was the purpose of the present invention, though the art can be used with all trampolines.  
         [0005]     Low performance backyard trampolines are used very differently than high performance trampolines used by skilled competitors for training and competition. For instance, many on-bed backyard trampoline injuries occur when multiple jumpers are using the trampoline at the same time as reported in the NEISS data compiled by the CPSC. Because children enjoy playing together most families allow more than one child to jump at the same time even though this practice is strongly discouraged by trampoline manufacturers, the CPSC, and others experts. Competition trampolines are used almost exclusively in disciplined environments for the structured teaching of specific skills. In contrast, backyard trampolines are largely used for fun, unstructured, imaginative play activities that are relished by kids and recommended by child development experts who understand that daily physical activity significantly enhances learning ability and that kids need activities to counterbalance today&#39;s over-structured and sedentary lifestyles. Unfortunately, these unstructured trampoline activities generate numerous on-bed injuries when jumpers land on the rebounding surface in an awkward body position or when a jumper lands on a trampoline bed that has been preloaded with the energy from other jumper impacts.  
         [0006]     There thus remains a need to significantly reduce the quantity and severity of on-bed injuries that result from such playful activities. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     In the drawings:  
         [0008]      FIG. 1  is an oblique view of a dual position fastener system.  
         [0009]      FIG. 2  is an oblique view of the system of  FIG. 1  showing the fastener system used on a trampoline. 
     
    
     DETAILED DESCRIPTION  
       [0010]     A system that embodies a new use for adjustable or extendable springs is provided. Completely counter to using adjustable or extendable springs to equalize the tension between all the springs as conceived by the prior systems, the present system uses adjustable springs to systematically vary the tension between the springs. For example, removing most of the tension on every other spring (half of the total number of springs) while they are at rest makes the bed safer by changing its rebounding dynamics.  
         [0011]     All things being equal, varying the spring tension this way is more effective than the prior art at preventing on-bed injuries that result from multiple jumpers and awkward landings. For instance, many injuries occur when multiple users are jumping asynchronously, a first jumper deflects the bed and loads springs with the energy from his fall and now a second jumper lands on the bed in an awkward position. At this point in time, the bed is highly tensioned (unforgiving) and has just begun moving rapidly upward, recycling the energy loaded into the springs by the first jumper. In this case a bed supported by springs with varied tensions or limits of elasticity could be used to significantly reduce the impact force being experienced by the second jumper, thereby helping to prevent an injury. On a standard trampoline bed it takes less time for the bed to transition from moving down (absorbing energy) to moving up (releasing, recycling energy) precisely because all of the springs are uniformly tensioned and working in concert. On the other hand, a bed using springs that vary in tension takes longer to transition because the springs are not working in concert; half the springs are fully loaded and ready to begin releasing energy while the other half are not fully loaded and still capable of absorbing more energy. With only half of the springs fully loaded, the bed is more forgiving because it can absorb the second jumper&#39;s impact more slowly; the bed has a greater capacity to absorb energy more slowly because half of its springs are not fully loaded.  
         [0012]     This extended absorption time helps to prevent injuries in three ways: 1) It allows the jumper more time to reposition his body into a less awkward or injury-prone position. 2) It allows more time for the energy from an impact to transfer throughout the body thereby lessening the stress in any localized area. 3) It allows the mat to conform more completely to the user&#39;s body; it allows more of the mat to come in contact with the user&#39;s body, spreading the load over a larger area and thereby lessening the load on a given area, or point of the body. All things being equal, at any point during a rebound cycle, a bed with varied spring tensions will always be more forgiving (will always take more time to absorb an equal amount of energy) than a standard bed. The primary function of the system is to provide a “softer”, more cushioned or better shock-absorbing surface than a traditional bed.  
         [heading-0013]     The Springs are Phased in or Staged  
         [0014]     There are numerous methods for systematically varying the tension (or the travel distance required to reach limit of elasticity) between adjacent (or sets of adjacent) springs  10 . In a preferred embodiment, the length of the V-rings  12  or the connectors that are located between the bed and the springs is varied, such as can be seen in  FIGS. 1-2 , so that every other spring is more (or less) tensioned than the springs on either side of it. Similarly, the V-rings could be configured in repeating sets of three or more with long, middle, and short V-rings. A second embodiment uses two or more springs of the same dimensions except that the length varies. A third embodiment uses springs of various designs (back loaded and not back loaded, weaker and stronger, higher limit of elasticity and lower limit of elasticity). A fourth embodiment uses varied attachment points on the frame or bed; the spring anchor points can be moved in or out relative to the center of the trampoline [the shape of the tubing can be varied (oval, square, triangular) to simplify installation].  
         [0015]     A fifth embodiment uses cams of various sizes to alter the rebound dynamics. In each of these embodiments a number of elements can be varied to affect the performance.