Abstract:
A safer, more user-friendly spring-balance single-rider teeter-totter includes manual adjustments for both the vertical position of the spring, which adjusts the rest height of the seat, and the horizontal position of the spring from the pivot, which adjusts the counterbalance resistance. A safety cover may be provided for the spring or other counterbalance mechanism.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to field of amusement devices, particularly teeter-totters. Specifically, the invention relates to a spring balanced single rider teeter-totter. 
     2. Background 
     Teeter-totters, also known as seesaws, have long been popular items of playground equipment for children. Teeter-totters come in various configurations, but most are fundamentally similar. In the most basic configuration, a teeter-totter can be simply a plank supported near its center for pivotal movement. 
     A variation of the conventional two-rider teeter-totter is one adapted for use by a single rider. One-sided, single-rider teeter-totters typically consist of a pivoting seat with a counterbalance, such as a spring, to balance the rider&#39;s weight. The rider rides up and down on the seat in a bouncing manner against the elastic resistance of the spring or other counterbalance device. An early version of a single rider teeter-totter is shown in U.S. Pat. No. 1,586,254. This device has a board with a seat at one end and a pivot near the opposite end. A spring is attached at the extreme opposite end of the board to balance the rider&#39;s weight. The height of the pivot and, indirectly, the counterbalancing effect of the spring is adjusted by raising or lowering a pair of threaded boards that support the pivot. This is a cumbersome adjustment and weakens the structural integrity of the frame. Furthermore, there is no direct adjustment for the resistance of the spring, nor is there any safety cover for the spring. 
     Other prior art single rider teeter-totters, including, for example, the device shown in U.S. Pat. No. 3,968,962, disclose adjustments for the spring resistance, that require that the spring or springs be repositioned. The adjustment process requires that the seat be lifted to release any tension and that the spring then be disconnected and reattached at a different location. In some of the prior art devices, the spring or springs must be moved from one detent to another, or the point of attachment of the spring must be slid along a track. These prior art methods of adjusting the spring tension are both cumbersome and dangerous. If the springs become detached or dislocated during use of the teeter-totter, the counterbalancing force may be reduced or eliminated altogether causing the rider to strike the ground forcibly and unexpectedly. Furthermore, fingers can be easily pinched while manually adjusting the springs. 
     SUMMARY OF THE INVENTION 
     The present invention provides a safer, more user-friendly single rider teeter-totter. Manual adjustments are provided for both the vertical position of the spring, which adjusts the rest height of the seat, and the horizontal position of the spring from the pivot, which adjusts the counterbalance resistance. Adjustments are accomplished with lead screw mechanisms, which provide virtually infinite adjustment within the travel of the screw and which remain in a selected position without the need for locks or detents. Other embodiments may include a locking slide mechanism that positively locks in defined detent positions. A safety cover may be provided for the spring or other counterbalance mechanism. Indicators are provided for visual reference of the adjustments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a single rider teeter-totter in accordance with an embodiment of the present inventions. 
         FIG. 2  is a detailed view of the height adjustment for the counterbalance mechanism. 
         FIG. 3  is a detailed view of the position adjustment for the counterbalance mechanism. 
         FIG. 4  is a detailed view of an optional shroud for the counterbalance mechanism. 
         FIG. 5  is a detailed view of an optional secondary elastic counterbalance. 
         FIG. 6  is a detailed view of an alternative position adjustment for the counterbalance mechanism. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, for purposes of explanation and not limitation, specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known methods and devices are omitted so as to not obscure the description of the present invention with unnecessary detail. 
       FIG. 1  is a perspective view of a single rider teeter-totter  10  in accordance with an embodiment of the present invention. A frame  12  comprises forward support member  14  and generally U-shaped rear support member  16 . The frame further comprises pivot support post  18  with pivot assembly  20  attached at the top thereof. Longitudinal beam  22  is coupled to pivot assembly  20 . Seat support member  24  is attached to beam  22 . The various components of frame  12  may be fabricated from tubular steel as is common for exercise and playground equipment, although other materials may be used if desired. 
     Seat  26  is attached to seat support member  24 . Seat  26  may be constructed of a molded foam or plastic material. A handle bar  28  is attached to the upper portion of seat support member  24 . The weight of a rider in the seat  26  is counterbalanced by springs  32 . A pair of springs is used in parallel so that if one of the springs fails, the second spring will still provide half of the counterbalancing force to prevent the teeter-totter from falling uncontrollably. In the event of a spring failure, or if the spring resistance is not properly adjusted, or if the rider is simply overly exuberant, impact with the ground is cushioned by bumper  30  attached to seat support member  24 . Furthermore, the design of generally U-shaped rear support member  16  ensures that the rider will not contact any of the frame members at the bottom limit of travel and also eliminates pinch points in the vicinity of the seat. 
       FIG. 2  illustrates the spring height adjustment mechanism, which sets the rest height of the seat and thereby also acts as a range of travel adjustment. This mechanism adjusts the lower attachment point of springs  32  and thereby adjusts the height of seat  26  off of the ground. Yoke  34  is attached to forward support member  14  and carries adjustment screw  36 . The lower ends of springs  32  are attached with chain links  33  to follower  38 , which is threadably engaged on adjustment screw  36  and slides within guides  39 . Knob  40  is used to manually rotate adjustment screw  36 , thereby raising or lowering follower  38 . A numerical indicator  41  may be provided to assist riders in setting the seat height at a desired level. Guides  39  prevent twisting of the springs  32  as the vertical position of follower  38  is adjusted. This type of a lead screw adjustment mechanism provides virtually infinite adjustment within the travel of follower  38  on screw  36  and remains in a selected position without the need for any additional locking or detent mechanism. 
     The chain links  33  constitute flexible couplings that communicate tensile forces, but not compressive forces. As the rider approaches the top of the range of movement, the springs become fully relaxed and the chain links allow for continued upward movement. The rider thus experiences a free-floating or weightless sensation at the top of the range of movement. 
       FIG. 3  is a detailed view of the counterbalance adjustment mechanism. Adjustment screw  42  is suspended below beam  22 . The upper ends of springs  32  are attached to follower  44 , which is threadably engaged on adjustment screw  42 . Knob  46  is used to manually rotate adjustment screw  42 , thereby moving follower  44  fore and aft in relation to beam  22 . When follower  44  is moved closer to pivot  20 , the effective resistance of springs  32  is reduced, which is desirable for use of the apparatus by a lighter rider. Conversely, a heavier rider would turn knob  46  to move follower  44  further away from pivot  20 , thereby increasing the effective resistance of springs  32 . A numerical indicator may be provided on beam  22  as illustrated to assist riders in setting the effective resistance to a desired value. 
       FIG. 4  shows an optional elastic shroud  50  that surrounds the springs  32 . This protects children from having their fingers or other parts of their bodies pinched by the springs as they stretch and relax. 
       FIG. 5  shows an optional secondary counterbalance  52 . This may be an elastic cord that provides additional counterbalancing force in the event that one or both of the springs breaks. Cord  52  is coupled in parallel with the springs  32  and may be threaded though the center of one of the springs if desired. Cord  52  could also be inelastic to serve as a safety tether to stop the downward movement of the seat before it strikes the ground. 
       FIG. 6  shows an alternative counterbalance adjustment mechanism. Here, longitudinal beam  22 ′ is notched with detents  65  along a portion of its length. Springs  32  are attached to slider  60 , which rides along beam  22 ′ and is configured to be gripped by hand. A trigger  62  is pivotally attached to slider  60  and is biased towards an engaged position by spring  64 . Squeezing trigger  62  releases detent lock  66  from engagement with detent  65  and allows slider  60  to be moved forward or rearward to a desired position. As in the previously described embodiment, a numerical indicator may be provided on beam  22 ′ as illustrated to assist riders in setting the effective resistance to a desired value. 
     It will be recognized that the above-described invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the disclosure. Thus, it is understood that the invention is not to be limited by the foregoing illustrative details, but rather is to be defined by the appended claims.