Patent Document

PRIORITY AND INCORPORATION BY REFERENCE 
       [0001]    This application claims the priority and benefit of U.S. Provisional Application No. 62/019,538, filed Jul. 1, 2014, which is hereby incorporated by reference herein in its entirety for all purposes. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally relates to pogo sticks, and more specifically to pneumatic pogo sticks. 
         [0004]    2. Description of the Related Art 
         [0005]    A conventional pogo stick utilizes a coil spring within a hollow tube housing to create an upward force when compressed by a user to propel the user in an upward direction. In order to get more lift than can be provided with a coil spring and without increasing the weight of the pogo stick itself, it has been recognized in the art that an air filled cylinder/piston arrangement can produce increased propulsion or lift for the same length of stroke. Some have gone so far as incorporating engine power in order to increase lift and provide a powered jumping stick. 
         [0006]    Various attempts have been made in the art to provide pneumatic pogo sticks. One example of an air-type pogo stick includes a cylinder to which foot-boards are attached in a body. The cylinder has a valve through which a user can regulate the space within the cylinder. The pogo stick is simultaneously worked by both pressure power and vacuum power created in the upper and lower part of the piston in the cylinder respectively when exerted by an outside force. Such a pogo stick, however, has many shortcomings in both construction and functionality and fails to address many of the problems encountered when attempting to use compressed air as a spring. 
         [0007]    Pogo stick users have creatively learned to do pogo stick tricks while they are propelled upward. Extreme tricks are common now in many official sports, such as snowboarding, skateboarding, and extreme motorsports, and many users have implemented extreme tricks on pogo sticks. Thus, it would be advantageous to provide a pneumatic pogo stick that allows for relatively smooth jumping and landing while allowing the user to obtain greater height to have more hang-time for more creative and complicated tricks. 
       SUMMARY 
       [0008]    The systems, methods and devices described herein have innovative aspects, no single one of which is indispensable or solely responsible for their desirable attributes. Without limiting the scope of the claims, some of the advantageous features will now be summarized. 
         [0009]    In some embodiments, the pogo stick may comprise a housing, a sliding shaft, and a piston. The piston may be connected to the sliding shaft and the sliding shaft may be disposed in the housing. The sliding shaft may define a hollow chamber that fluidly communicates with a space between the piston and the housing. 
         [0010]    In some embodiments, the pogo stick may comprise a housing, a sliding shaft, and a piston. The piston may be connected to the sliding shaft and the sliding shaft may be disposed in the housing. The piston may define a concave shape. An upper surface of the piston may be concave. Portions of the piston may define a void, such that a space between the piston and the housing may include the void. The piston may be cup-shaped. 
         [0011]    In some embodiments, the pogo stick may comprise a housing, a sliding shaft, and a piston. The piston may be connected to the sliding shaft and the sliding shaft may be disposed in the housing. The piston may define a concave shape. The sliding shaft may define a hollow chamber that fluidly communicates with a space between the piston and the housing. 
         [0012]    In some embodiments, the pogo stick may comprise a housing, a sliding shaft, and a piston. The piston may be connected to the sliding shaft and the sliding shaft may be disposable in the housing. The piston may comprise one or more structural supports that extend in a generally upward direction and may contact a wall of the housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The above-mentioned aspects, as well as other features, aspects, and advantages of the present technology will now be described in connection with various embodiments, with reference to the accompanying drawings. The illustrated embodiments, however, are merely examples and are not intended to be limiting. Like reference numbers and designations in the various drawings indicate like elements. Not all of the elements of the drawings are in to scale relate to other drawings and the comparative size of one element relative to another element in the drawings is not necessarily indicative of the relative sizes of the elements in one or more embodiments. 
           [0014]      FIG. 1  shows a side elevational view of an embodiment of a pneumatic pogo stick. 
           [0015]      FIG. 2  shows a side elevational cross-section view of a pogo stick. 
           [0016]      FIG. 3  shows a side elevational cross-section view of part of a pogo stick. 
           [0017]      FIG. 4  shows a side elevational cross-section view of at least a piston. 
           [0018]      FIG. 5A  shows a top, front, and side perspective view of a first embodiment of a hollow piston. 
           [0019]      FIG. 5B  shows a top, front, and side perspective view of a first embodiment of a hollow piston. 
           [0020]      FIG. 5C  shows a side elevational view of a first embodiment of a hollow piston. 
           [0021]      FIG. 5D  shows a top, front, and side perspective cutaway view of a first embodiment of a hollow piston. 
           [0022]      FIG. 6  shows a side elevational cutaway view of a second embodiment of a hollow piston. 
           [0023]      FIG. 7A  shows a side elevational cross-section view of at least a piston comprising a support structure. 
           [0024]      FIG. 7B  shows a top plan view of a piston comprising a support structure. 
           [0025]      FIG. 8A  shows a side elevational cross-section view of a third embodiment of a hollow piston. 
           [0026]      FIG. 8B  shows a side elevational cross-section view of a fourth embodiment of a hollow piston. 
           [0027]      FIG. 8C  shows a side elevational cross-section view of a fifth embodiment of a hollow piston. 
           [0028]      FIG. 8D  shows a side elevational cross-section view of a piston comprising a support structure. 
           [0029]      FIG. 8E  shows a side elevational cross-section view of a piston comprising a support structure. 
           [0030]      FIG. 9A  shows a side elevational see-through view of one embodiment of a hollow piston 
           [0031]      FIG. 9B  shows a side elevational cutaway view of one embodiment of a hollow piston. 
           [0032]      FIG. 10A  shows a side elevational view of one embodiment of a piston comprising a support structure. 
           [0033]      FIG. 10B  shows a side elevational isometric view of one embodiment of a piston comprising a support structure. 
           [0034]      FIG. 11A  shows a side elevational cross-section view of one embodiment of an air shaft. 
           [0035]      FIG. 11B  shows a side elevational cross-section view of one embodiment of an air shaft. 
           [0036]      FIG. 12A  shows a side elevational cross-section view of one embodiment of an air shaft. 
           [0037]      FIG. 12B  shows a side elevational cross-section view of one embodiment of an air shaft. 
       
    
    
     DETAILED DESCRIPTION 
       [0038]    One patent, U.S. Pat. No. 7,011,608, is incorporated by reference in its entirety for all purposes. It discloses an invention that utilizes a pneumatic spring, which includes a piston/cylinder with user graspable handles attached or coupled relative to the top of the cylinder, and an elongated shaft attached to the bottom of the piston. Thus, stepping or jumping on the foot supports pushes the piston upward, compressing the air inside the cylinder. This compressed air acts like a spring creating a force on the piston, thus forcing the piston and the attached shaft away from the handles, which in turn propels the cylinder, the foot supports attached thereto, and, ultimately, the user. Such a pneumatic pogo stick has a potentially higher power to weight ratio than a comparable coil spring pogo stick, and has a maximum compression ratio that helps provide smooth jumping and landing. 
         [0039]    In the following detailed description, reference is made to the accompanying drawings, which form a part of the present disclosure. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and form part of this disclosure. For example, a system or device may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, such a system or device may be implemented or such a method may be practiced using other structure, functionality, or structure and functionality in addition to or other than one or more of the aspects set forth herein. Elements that are described as “connected,” “engaged,” “attached,” or similarly described, shall include being directly and/or indirectly connected, engaged, attached, etc. Alterations and further modifications of the inventive features illustrated herein, and additional applications of the principles of the inventions as illustrated herein, which would occur to one skilled in the art and having possession of this disclosure, are to be considered within the scope of the invention. 
         [0040]    Descriptions of unnecessary parts or elements may be omitted for clarity and conciseness, and like reference numerals refer to like elements throughout. In the drawings, the size and thickness of layers and regions may be exaggerated for clarity and convenience. 
         [0041]    Features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. It will be understood these drawings depict only certain embodiments in accordance with the disclosure and, therefore, are not to be considered limiting of its scope; the disclosure will be described with additional specificity and detail through use of the accompanying drawings. An apparatus, system or method according to some of the described embodiments can have several aspects, no single one of which necessarily is solely responsible for the desirable attributes of the apparatus, system or method. After considering this discussion, and particularly after reading the section entitled “Detailed Description” one will understand how illustrated features serve to explain certain principles of the present disclosure. 
         [0042]    As shown in  FIGS. 1 and 2 , a pneumatic pogo stick  100  may comprise a main tube or housing  105 , a sliding shaft  110 , a piston  115 , a handle  120 , and foot rests  125 . The sliding shaft  110  may generally be configured to move in and out of the housing  105  in a longitudinal direction. In some embodiments, the longitudinal direction of the movement of the sliding shaft  110  may be substantially parallel to the longitudinal axis of the housing  105 . A handle  120  may be connected to the top of the housing  105 . The handle  120  may serve the purpose of allowing a user to grip the pogo stick  100 . Foot rests  125  may provide a location on which a user can stand. In some embodiments, the housing  105  comprises a generally cylindrical shape, although the housing  105  may comprise other shapes such as frustoconical, square, hexagonal, octagonal, or other similar shape. The sliding shaft  110  may comprise a generally cylindrical shape, or some other shape, such as square, hexagonal, octagonal, or some other shape. The handle  120  and/or foot rests  125  may be temporarily or permanently attached to the housing  105 . 
         [0043]    In some embodiments, the pneumatic pogo stick  100  is used by a user gripping the handle  120  and stepping onto the foot rests  125 , and then moving in an up-and-down motion. As the user and the pogo stick  100  impact the ground, the sliding shaft  110  may have a tendency to slide up and into the housing  105 . In some embodiments, the space within the housing above the piston  130  is reduced. If air or another gas is trapped in that confined space  130 , the pressure of that gas may increase. The increase in pressure may store potential energy, which may exert a force on the top of the piston  115  pushing down, as well as on the top of the housing  105  pushing up. When the sliding shaft  110  is inserted into the housing  105 , the user may push down on the foot rests  125  simultaneously to the gas pushing up on the top a housing  105 , which may help propel the user and pogo stick  100  in a generally upward direction. This process may be repeated more than once, and may be repeated indefinitely. 
         [0044]    The housing  105  may comprise PVC, polycarbonate, metal, plastic, or other material, and may be created through casting, extruding, welding, or other various manufacturing techniques. The wall thickness of the housing  105  may be between a few millimeters and one or more centimeters thick. In some embodiments, it may be advantageous for the housing  105  to be lightweight, and this may be accomplished using generally lightweight materials and/or a thinner wall thickness. 
         [0045]    With reference to  FIG. 3 , the piston  115  may comprise a device which substantially interacts with the inside wall of the housing. In some embodiments, a gasket or seal  135  may be present which may help prevent gases from moving around the piston  115 , for example from the confined space  130  to below the piston  115 . The piston  115  may form various shapes depending on the application. A bumper  140  may be disposed below the piston  115  and above a bushing  145 , such that when the sliding shaft  110  extends out from the housing  105 , the bottom of the piston  115  may impact or contact the bumper  140 . The bumper  140  may serve the function of limiting the travel of the sliding shaft  110  and/or piston  115 , and may help prevent damage to any of the parts. The bumper  140  may comprise rubber, plastic, nylon, or other various materials that may serve the function of limiting the motion of the sliding shaft  110  and/or piston  115 , and prevent any of the moving parts from damage. Further, a spacer  150  may be disposed between the bumper  140  and the bushing  145 . The spacer  150  may comprise plastic, nylon, or other various materials. 
         [0046]    In some embodiments, a bushing  145  may be disposed at the bottom of the housing  105  near the foot rests  125 , and below the bumper  140  and/or spacer  150 . When the sliding shaft  110  is fully extended, the bumper  140  may be disposed between the bottom of the piston  115  and the top of the bushing  145 . The bushing  145  may comprise an aperture through which the sliding shaft may travel. The bushing  145  may help keep the sliding shaft  110  aligned, such that the sliding shaft  110  does not rotate coaxially to the housing  105 . For instance, the cross-section of the sliding shaft  110  may be generally square, and the aperture in the bushing  145  may also be square. This configuration may prevent the sliding shaft  110  from substantially spinning around or turning. The bushing  145  may also help prevent the sliding shaft  110  from rotating about an axis perpendicular to an axis of the housing  105 . The bushing  145  may comprise a metal or other generally rigid material, and may define an aperture through which the sliding shaft  110  may travel. The bushing  145  may be temporarily or permanently attached to the housing, and in some instances may be pressed fit to the housing  105 . For instance, as a non-limiting example, when the user and the pogo stick  100  are impacting a surface, the sliding shaft  110  may be in a fully extended position and have maximum exposure outside of the housing  105 . If the user and the pogo stick  100  do not land in an exactly vertical direction, the force of the ground on the sliding shaft  110  may not be parallel to the direction of travel of the user and the housing  105 . In such an instance, the housing  105  may have a tendency to rotate about an axis generally horizontal and may place a bending force on at least part of the sliding shaft  110 . It may be advantageous to reinforce the sliding shaft  110  with a bushing  145  in order to resist this bending force. 
         [0047]    In some embodiments, the sliding shaft  110  may comprise a bounce pad  155  at the bottom of the shaft  110 , and may generally contact the surface or ground upon which the pogo stick  100  is used. The bounce pad  155  may comprise a plastic, rubber, or other material. The bounce pad  155  may serve the purpose of gripping the ground surface, such that upon impact, the bounce pad  155  and/or sliding shaft  110  do not slip out from under the user. Additionally, the bounce pad  155  may help insulate the user from vibration or other forces. The bounce pad  155  may be attached to the sliding shaft  110  using glue, screws, bolts, or other various attachment methods. 
         [0048]    In some embodiments, the top of the housing  105  may be sealed by a cap  160  that may be temporarily or permanently attached to the housing  105 . The cap  160  may be attached using bolts, adhesives, chemicals, welding, or other attachment methods. The cap  160  may comprise a valve (not shown) through which gases may be inserted into the housing  105 . The handles  120  may also be attached to the housing  105  and/or the cap  160 , such that use of the handles  120  by the user to hold onto the pogo stick device  100 , may not generally dislodge the handles  120  from the device. 
         [0049]    In some embodiments, the sliding shaft  110  generally travels into and out of the housing  105 , beginning at a maximum extension, and ending at a maximum compression. The maximum extension may be defined as the configuration when the sliding shaft  110  is slid out of the housing  105  as far as, or nearly as far as, the sliding shaft  110  can travel. Maximum compression may be defined as the configuration when the sliding shaft  110  is disposed into the housing as far as, or nearly as far as, possible. In these configurations, the volume of space  130  may comprise the volume above the piston  115 , and below the cap  160 , that is confined within the housing  105 . In some embodiments, the volume of space  130  may comprise a gas, air, or specific gases such as nitrogen. Different gases at different pressures may be advantageous. For instance, as a non-limiting and illustrative example, the volume of space  130  may be filled with gas at a pressure higher than atmospheric pressure. The compression ratio may be defined as the volume of space  130  when the sliding shaft  110  is at an extension position divided by the volume of space  130  when the sliding shaft  110  is at a compression position. For instance, if the volume of space  130 , when the sliding shaft  110  is an extension position is 20 in. 3 , and the volume of space  130 , when the sliding shaft  110  is at a compression position is 5 in. 3 , then the compression ratio is 20÷5, or 4. This compression ratio may be, therefore, a function of at least the stroke length of the sliding shaft  110 , the volume of space above the piston  130  at the extension position, and the volume of space above the piston  130  at the compression position. The compression ratio may also be a factor of the diameter of the housing  105  and the length of the housing  105 . 
         [0050]    A “hammering” effect may be caused when the pressure inside a compression chamber increases rapidly due to too high of a compression ratio. This effect is common in water pipes when a fluid in motion is forced to stop or change direction suddenly causing a large momentum change. When “hammering” happens on a pogo stick, the sudden change in pressure inside the chamber may also cause problems for the pogo stick user. This effect, however, can be reduced by modifying the compression ratio. This can be done in many ways including changing the stroke length such that at maximum compression the sliding shaft  110  is not disposed as far into the housing  105 . This may increase the volume of space above the piston  130  at maximum compression, which may lower the compression ratio. 
         [0051]    As used in this disclosure, the term “piston” should generally be given its plain and ordinary meaning of an object that fits snugly into a larger cylinder or tube and moves under fluid pressure. Variations to the shapes of the piston and/or the cylinder may be accomplished without deviating from the scope of the invention. For instance, as a non-limiting example, the piston shape may be elliptical in order to match the elliptical cross-sectional shape of the cylinder. The term “compression ratio” should generally be given its plain and ordinary meaning of the ratio of the volume between the piston and cylinder head before and after a compression stroke. In the case of a pogo stick, the compression stroke may comprise the sliding shaft moving from an extended position to a compressed position. The “maximum compression ratio” may be defined as the ratio of the volume between the piston and cylinder head before and after a compression stroke, when the piston travels from the maximum extension position to the maximum compression position. In embodiments with a maximum compression ratio, other compression ratios for the same embodiments may be possible, depending at least on the stroke length of the sliding shaft. 
       Hollow Sliding Shaft 
       [0052]    In some embodiments, the sliding shaft  110  may be configured to comprise a hollow chamber  205  inside and an opening  210  from the hollow chamber  205  through the piston  115 , such that the volume of space  130  above the piston  115  fluidly communicates with the hollow chamber  205  inside the sliding shaft  110 . This configuration may increase the volume of space  130  at maximum compression, which may decrease the compression ratio. The volume of space  130  may include both the space above the piston  115 , between the piston  115  and the cap  160 , as well as the volume of space within the sliding shaft  110  that fluidly communicates with the space above the piston  115 . As shown in  FIG. 4 , the piston  115  may be attached to the top of the sliding shaft  110 , and air may move from above the piston  115 , through the piston  115 , and into the hollow chamber  205  inside the sliding shaft  110 . When the user compresses the volume of space  130  by jumping on the foot supports  125 , the piston  115  compresses the air inside the cylinder above the piston  115  and within the hollow chamber  205  in the sliding shaft  110 . 
         [0053]    To illustrate by example, a pogo stick  100  without the hollow space  205  in the sliding shaft  110  may have a piston  115  with a stroke length of 18 inches, and 2 inches of length above the piston  115  at compression. The inside diameter of the housing  105  may be 3 inches (and a radius of 1.5 inches). The volume of a cylinder is (height)×(II)×(radius squared). At extension, the volume of space  130  would be (18+2)(3.14)(1.5 2 ) or 141.3 in 2 . At compression, the volume of space  130  would be (2)(3.14)(1.5 2 ) or 14.1 in 2 . Therefore, the compression ratio would be 10:1. However, the volume of the hollow chamber  205  inside square sliding shaft  110  may be 1 inch by 1 inch by 25 inches long, or an additional 25 in. 3  of space, which may be added to the volume of space at extension and compression. Therefore, the compression ratio would be (141.3+25):(14.1+25) or 4.25. Other compression ratios may be possible depending at least on the stroke length, volume of space  130  above the piston  115  at compression, diameter of the cylinder  105 , and volume of the hollow chamber  205  inside the sliding shaft  105 . 
         [0054]    In some embodiments, a spacer  150  is added between the bottom of the piston  115  and the bushing  145  (see  FIG. 3 ). This spacer  150  may help prevent the piston  115  from coming too close to the bushing  145 . If the piston  115  gets too close to the bushing  145 , for instance when the sliding shaft  110  is at extension, then the sliding shaft  110  may have a tendency to bend at the bushing  145  or damage the piston  115  due to excessive force. The spacer  150  may create a longer moment arm of the sliding shaft  110  above the bushing  145 , which may reduce the force on the side of the piston  115 . 
         [0055]    In addition to possible damage to the piston  115  or sliding shaft  110 , a piston  115  being too close to the bushing  145  may increase friction between the piston  115  and the housing  105  and slow down the compression stroke. For instance, as a non-limiting example, if the piston  115  is too close to the bushing  145  when the sliding shaft  110  begins travel from an extension position, excessive force may be applied to the piston  115  by the cylinder wall. This increase in force may increase the friction between the piston  115  and cylinder wall, which may produce drag as the piston  115  moves through the housing  105  from the extension position to the compression position. The drag may decrease the speed at which the piston  115  travels, and may prevent the piston  115  from reaching the maximum compression position. In order to alleviate this drag, a spacer  150  may be placed between the bumper  140  and the bushing  145 , which may prevent the piston  115  from getting too close to the bushing  145 , and thus reducing the amount of drag experienced by the piston  115  during the compression stroke. 
         [0056]    With reference to  FIGS. 11A and 11B , two embodiments of a hollow sliding shaft are shown. Both embodiments have a shaft sidewall  1101 . The sidewall  1101  may be configured to have cross-sections of various shapes. For example, sidewall  1101  may have a generally square cross-section, such that the hollow sliding shaft slides through a bushing with a square opening during compression and extension. This feature would allow the bushing to keep the hollow sliding shaft from rotating. Both embodiments shown have a piston plate  1103 . The piston may rest atop piston plate  1103 , and in some embodiments piston plate  1103  may have a means for connecting the hollow sliding shaft to the piston. For example, piston plate  1103  may have threads that correspond to matching threads at the bottom of the piston. In that manner, piston plate  1103  may be engaged with the piston so that the hollow sliding shaft moves with the piston during compression and extension. 
         [0057]    At the top of the hollow sliding shaft may be a pipe close nipple  1105 . Pipe close nipple  1105  may allow air to move from the cylinder down into the hollow chamber  1117  within the sliding shaft, and it illustrates just one mechanism for doing so. The mechanism may be any kind of valve or opening configured to provide fluid communication between the cylinder and the hollow chamber  1117  within the sliding shaft. Here, the pipe close nipple  1105  may also serve as a way for the sliding shaft to attach to the piston. The pipe close nipple  1105  may be the portion that attaches to the piston, such as through the use of threads on pipe close nipple  1105  designed to engage with complimentary threads disposed within the piston. 
         [0058]    At the bottom of the sliding shaft shown is  FIG. 11A  is opening  1107 . Opening  1107  may instead be sealed off, as shown in  FIG. 11B . The bottom of the sliding shaft in  FIG. 11B  is sealed in order to trap air within the hollow chamber  1117  in the sliding shaft. This allows for additional air storage within the sliding shaft to help create a softer, smoother, and easier bounce for the rider. The exact amount of additional air volume depends on a shaft length, and cross-sectional area of the shaft sidewall  1101 . As a non-limiting example, in some designs the addition of a hollow sliding shaft provides for an additional 20 in3 of air storage. 
         [0059]    The exact method of sealing off the bottom of the shaft may vary.  FIG. 11B  shows an embodiment with a welded-in plug  1109 . There is a threaded plug  1111  below, with a quarter-inch gap  1115  between the two plugs  1109  and  1111 . The threaded plug  1111  may have an opening or means for a bounce bad to be connected to the sliding shaft. For example, threaded plug  1111  has an opening  1113  through which a bounce pad may be screwed or bolted into place. The quarter-inch gap  1115  may allow for additional space so that a bolt can be threaded all the way through the threaded plug  1111  in order to be locked tightly in place. 
         [0060]    With reference to  FIGS. 12A and 12B , different embodiments of the sliding shaft are further shown. The figures show a piston plate  1201 , which may have a means for connecting to the piston such as threads  1201  which may match complimentary threads disposed within the piston. These embodiments do not have a pipe close nipple or valve mechanism. Instead, top opening  1211  shown in  FIG. 12B  may be a mechanism through which air can move from the cylinder into the hollow space within the sliding shaft. 
         [0061]      FIG. 12A  has an opening  1205  at the bottom of the shaft. However,  FIG. 12B  is an embodiment where plug  207  is welded into the bottom of the shaft. Plug  207  has bolt socket  1209  in which a bounce pad may be screwed or bolted into place. This embodiment demonstrates how the bottom of the sliding shaft may be welded closed using a single plug, rather than multiple plugs that serve the purposes of welding closed the bottom of the shaft and providing a connection means for a bounce pad. 
       Hollow Piston 
       [0062]    In some embodiments, as shown in  FIGS. 5A-D  the piston  115  may be elongated such that it is several inches long. The center  305  of the piston  115  may be hollowed out or form a concave structure, such that the volume of space  130  above the piston  115  is increased by the amount of space  310  within the hollowed out or concave portion of the piston  115 . In these embodiments, the volume of space above the piston  130  is increased, when the sliding shaft is at maximum extension and at maximum compression. The volume of space  130  may include both the space above the piston  115 , between the piston  115  and the cap  160 , as well as the volume of space  310  within the piston  115  that fluidly communicates with the space above the piston  115 . This configuration may allow the compression ratio of the pogo stick  100  to decrease, similar to the decrease in compression when using a hollow chamber  205  in the sliding shaft  110 . The piston  115  may be elongated from the base  315  to the rim  320 , and may increase the length of the moment arm of the sliding shaft  115  above the bushing  145 . Thus, the spacer  160  may not be necessary. The piston  115  may comprise a groove  325  into which a gasket or seal  135  may be placed. In some embodiments, this groove  325  may be located generally near the top rim  320  of the piston  115 . In some embodiments, the groove  325  may be located elsewhere, such as near the base  315  of the piston  115 . In some embodiments, the groove  325  may be located between the rim  320  and the base  315  of the piston  115 . 
         [0063]    For instance, as a non-limiting example, similar to the described above, a pogo stick  100  without a hollow piston  115  may have a maximum stroke length of 18 inches, and 2 inches of length above the top rim of the piston  115  at maximum compression. The inside diameter of the housing  105  may be 3 inches (and the radius of 1.5 inches). At maximum extension the volume of space  130  would be (18+2)(3.14)(1.5 2 ) or 141.3 in 2 . At maximum compression the volume of space  130  would be (2)(3.14)(1.5 2 ) or 14.1 in 2 . Therefore, the compression ratio would be 10:1. However, if the piston were 4 inches long and was hollowed out to have an inside diameter of 2.5 inches (and a radius of 1.25 inches), then the interior  305  of the piston  115  would add 19.63 in. 3  of additional space  310 , which may be added to the volume of space  130  at maximum extension and maximum compression. Therefore, the compression ratio would be (141.3+19.63):(14.1+19.63) or 4.77. Other compression ratios may be possible depending on the stroke length, volume of space  130  above the piston  115  at maximum compression, diameter of the cylinder, and volume  310  of the hollow piston  115 . 
         [0064]    With reference to  FIGS. 9A and 9B , different embodiments of the hollow piston  901  are shown. Both embodiments have an annular groove  903  in which an o-ring, seal, or gasket can be disposed. This prevents air from flowing around the sides of the hollow piston  901  and going below the piston. Both embodiments may have an overmolded portion  911 . The functional aspect of this overmolded portion  911  may be to conceal a means for connecting the piston to the shaft. For example, in  FIG. 9B , overmolded portion  911  has a bolt  913  that is overmolded into the bottom of the piston. This bolt  913  may be a way of connecting to a shaft. For example, the shaft may have a piston plate with a socket or recess that bolt  913  may slide into. 
         [0065]    The embodiment in  FIG. 9A  has an annular groove  903  that is comprised of an upper lip  905  and a bottom lip  907 . Upper lip  905  and bottom lip  907  serve to hold the seal in place within the annular groove  903 . 
         [0066]    The embodiment in  FIG. 9B  has an annular groove  903  that is comprised of upper lip  905  and a bottom lip  909 . Bottom lip  909  is thicker than the bottom lip  907  in  FIG. 9A . This thicker bottom lip  909  may reinforce the bottom lip  909  against the forces that are exerted upon it by the seal or o-ring during the compression or extension of the shaft. 
       Hollow Sliding Shaft and Hollow Piston 
       [0067]    In some embodiments, the hollow piston  115  may be combined with a hollow chamber  205  in the sliding shaft  110 , to increase the benefits. In these embodiments, the compression ratio may be decreased and/or the stroke length of the sliding shaft  110  may be increased. As shown in  FIG. 6 , a piston  115  may comprise a center  405  that may be hollowed out or form a concave structure, similar to embodiments described above. The piston  115  may comprise a volume of space  410  within the piston  115 , a base  415 , a top rim  420 , and a groove  425  that may be configured to accept a gasket or seal  135 . The piston  115  may additionally comprise an aperture  430  that goes through the bottom surface of the piston  115 . When the piston  115  is connected to the sliding shaft  110 , the aperture  430  may align with an opening in the sliding shaft, such that air in the hollow portion  410  of the piston  115  may fluidly communicate with the hollow portion  205  of the sliding shaft  110 . In some embodiments, the aperture  430  may comprise threads, such that the piston  115  can be threaded on to a portion of the sliding shaft  110 . 
         [0000]    Piston with Structural Supports 
         [0068]    With reference to  FIGS. 7A-8E , in some embodiments, a piston  115  may be elongated, with the gasket or seal  135  disposed near or at the base  505  of the piston  115 . Portions of the piston  115  may be removed in order to create more space for gases to occupy. However, portions of the elongated piston  115  may remain in order to preserve the preferred moment arm of the sliding shaft  110  near the bushing  145  when the sliding shaft  110  is at maximum extension. As shown in  FIG. 7A , the piston  115  may generally be disposed at the end of the sliding shaft  110 . The piston  115  may comprise one or more structural supports  510 , which may contact the cylinder wall above the end of the sliding shaft  110 . The structural supports  510  may be formed integral to the remainder of the piston  115 , or may be added during or after manufacturing. The structural supports  510  may comprise various configurations. As shown in  FIG. 7B , the structural supports  510  may generally radiate from a central location in the piston  115  and extend to the outer edge  515  of the piston  115 . 
         [0069]    As shown in  FIGS. 8A-E , the structural supports  510  may comprise various configurations. For instance, in  FIGS. 8A-C , the structural supports may comprise the wall sections of the piston  115  with at least portions of the center of the piston removed. In some embodiments, as shown in  FIGS. 8D and 8E , structural supports  510  may extend generally vertically from a central location on the piston  115 , with an upper end  520  of the supports  510  generally contacting the cylinder wall of the housing  105 . In these embodiments, the gasket or seal  135  may be located at or near the base  505  of the piston  115 . 
         [0070]    These embodiments may result in a decreased compression ratio. Alternatively one may maintain the same decreased compression ratio, while increasing stroke length of the sliding shaft  110 . In some embodiments, an increased stroke length may be advantageous to the user because it may allow a different jumping experience. For instance, as a non-limiting example, an increased stroke length may increase the distance over which the force from the ground and from the compressed gases act on the pogo stick  100  tending to direct in an upward direction. Since the same amount of potential energy is being released over a longer distance, the average forces acting on the user may decrease. This may make the pogo stick  100  easier to ride, safer, more enjoyable, and/or may have other benefits. In addition, one may decrease the compression ratio and thus reduce the hammering effect, which may have similar benefits. 
         [0071]    In various embodiments described herein, the piston  115  may be described as having a hollow portion or having portions of the piston removed. However, a person of skill in the art would recognize that the piston  115 , with the same or similar characteristics, may be produced by simply forming the piston  115  in the desired configuration, eliminating or reducing the need to remove any material. The description of a piston  115  with having material removed is intended to convey the structure of the piston  115 , and not to suggest a method of manufacturing, and the scope of the invention is not limited as such. 
         [0072]    With reference to  FIGS. 10A and 10B , alternate embodiments are shown for the piston  1003  comprising structural supports. Like in  FIGS. 7A-8E , the embodiments in  FIGS. 10A and 10B  also have a generally elongated piston shape. Portions of the piston  1003  may be removed in order to create more space for gases to occupy. Similar to the hollow piston embodiment, this allows for more air storage within the cylinder and tends to reduce the compression ratio. As a non-limiting example, the configuration depicted in  FIG. 10A  or  10 B may add about 8 in3 of additional air storage space within the cylinder, in comparison to a similarly shaped hollow piston embodiment. 
         [0073]    The overall structural frame of piston  1003  consists of the top portion of the piston  1001  which comprises an annular shape. The middle portion of the piston  1005  may also have an annular shape and be coaxial to the top portion of the piston  1001 . However, top portion of the piston  1001  may be wider than the middle portion of the piston  1005 , in order to be firmly seated within the diameter of the cylinder and to keep the piston  1003  from wobbling within the cylinder. In fact, this overall structural frame of the piston  1003  may be necessary to keep the shaft (not pictured) from being able to wobble side to side. Allowing the shaft to wobble from side to side may cause a number of issues, such creating gaps between the seal and the cylinder wall that may allow air to escape from the cylinder. 
         [0074]    The top portion of the piston  1001  and the middle portion of the  1005  in the overall structural frame of piston  1003  may be fixed together via one or more vertical structural supports  1011 .  FIGS. 10A and 10B  illustrate four vertical structural supports  1011  used to preserve the generally elongated, cylindrical shape of piston  1003 . However, this is just a non-limiting example. There may be any number of vertical structural supports  1011  used in the overall structural frame of piston  1003 . As examples, there could be two, three, five, six, and so forth, vertical structural supports  1011 . In a similar fashion, there may be any number of annular-shaped supports in the overall structural frame of piston  1003 , not just the two annular-shaped supports embodied in the top portion of the piston  1001  and the middle portion of the piston  1005 . There could be zero, one, three, and so forth, annular-shaped supports. The total amount of vertical structural supports  1011  and annular-shaped support members may be chosen in order to minimize the amount of space taken up by the overall structural frame of piston  1003 , while still providing the desired structural support to the piston  1003  to prevent the shaft from being able to wobble side to side. 
         [0075]      FIGS. 10A and 10B  further illustrate how an o-ring, gasket, or seal may be disposed within the groove of base  1007  of the piston, for the purpose of preventing gases from moving below the piston. In this configuration, this seal has been moved from the top of the piston to the bottom or base of the piston in order to prevent gases from moving below the piston. There may also be an overmolded portion  1009  of the base. This overmolded portion  1009  may allow for a way for the piston to be attached to the air shaft, such as by allowing a bolt to be overmolded into this overmolded portion  1009  at the bottom of the piston. Overmolded portion  1009  may also allow for air to move from the cylinder to a sliding shaft connected to the piston. For example, overmolded portion  1009  may have an outlet, valve, or opening that allows the air in the cylinder to be in fluid communication attached to a sliding shaft that may be attached to the bottom of piston  1003 . 
       Terminology 
     Additional Embodiments 
       [0076]    Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein. Additionally, a person having ordinary skill in the art will readily appreciate, the terms “upper” and “lower” are sometimes used for ease of describing the figures, and indicate relative positions corresponding to the orientation of the figure on a properly oriented page, and may not reflect the proper orientation of the device as implemented. 
         [0077]    Certain features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable sub combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub combination or variation of a sub combination. 
         [0078]    Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results. 
         [0079]    In describing the present technology, the following terminology may have been used: The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to an item includes reference to one or more items. The term “ones” refers to one, two, or more, and generally applies to the selection of some or all of a quantity. The term “plurality” refers to two or more of an item. The term “about” means quantities, dimensions, sizes, formulations, parameters, shapes and other characteristics need not be exact, but may be approximated and/or larger or smaller, as desired, reflecting acceptable tolerances, conversion factors, rounding off, measurement error and the like and other factors known to those of skill in the art. The term “substantially” means that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide. Numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also interpreted to include all of the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. As an illustration, a numerical range of “about 1 to 5” should be interpreted to include not only the explicitly recited values of about 1 to about 5, but also include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3 and 4 and sub-ranges such as 1-3, 2-4 and 3-5, etc. This same principle applies to ranges reciting only one numerical value (e.g., “greater than about 1”) and should apply regardless of the breadth of the range or the characteristics being described. A plurality of items may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. Furthermore, where the terms “and” and “or” are used in conjunction with a list of items, they are to be interpreted broadly, in that any one or more of the listed items may be used alone or in combination with other listed items. The term “alternatively” refers to selection of one of two or more alternatives, and is not intended to limit the selection to only those listed alternatives or to only one of the listed alternatives at a time, unless the context clearly indicates otherwise. 
         [0080]    It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the invention and without diminishing its attendant advantages. For instance, various components may be repositioned as desired. It is therefore intended that such changes and modifications be included within the scope of the invention. Moreover, not all of the features, aspects and advantages are necessarily required to practice the present invention. Accordingly, the scope of the present invention is intended to be defined only by the claims that follow. 
         [0081]    Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular embodiment. Conjunctions, such as “and,” “or” are used interchangeably and are intended to encompass any one element, combination, or entirety of elements to which the conjunction refers.

Technology Category: 1