Abstract:
A self-chargeable pneumatic cylinder comprises a cylinder body, a working piston disposed inside the cylinder body, and a hollow elongate shaft coupled to the working piston and extending outward from the cylinder body. The hollow interior of the shaft contains a pump mechanism for charging the pneumatic cylinder with a gas. The pump mechanism comprises a pumping piston that is axially slidable within the interior of the shaft and a pumping rod coupled to the pumping piston that is extendable out of the shaft for facilitating actuation of the pump. As the pump is manually actuated, pressurized gas flows into the cylinder body across a one-way valve to charge the pneumatic cylinder as desired.

Description:
RELATED APPLICATIONS  
       [0001]    The present application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 60/286,825, filed Apr. 27, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates generally to a pneumatic cylinder, and more particularly to a compact self-chargeable pneumatic cylinder.  
           [0004]    2. Background of the Invention  
           [0005]    Pneumatic cylinders are used in various applications such as air springs, actuation devices, and exercise equipment. Conventional pneumatic cylinders generally comprise a hollow cylinder body, a piston disposed in the interior of the cylinder body, and a shaft coupled to the piston that extends out of the cylinder body.  
           [0006]    Regardless of how a pneumatic cylinder is used, the gas chamber in the cylinder must be charged with a gas, such as atmospheric air, in order for the cylinder and piston arrangement to be operational. Various apparatuses and methods have been proposed wherein an external pump is used to charge the cylinder with a gas. However, in many situations, an external pump is not readily available due to the location of the cylinder, the mobility of the cylinder or the nature of the use. Furthermore, powered air pumps are only available in a very limited number of locations and manual pumps are burdensome to use and are often impractical to transport.  
           [0007]    In the past, attempts have been made to provide a self-chargeable pneumatic cylinder wherein a manual pump mechanism is attached to the cylinder such that the device is not dependent on an external pump. However, each of these attempts has fallen short because the self-chargeable pneumatic cylinders that have been proposed heretofore involve a large number of components thereby making the cylinders expensive to manufacture and prone to mechanical failures. In addition, each of the existing self-chargeable pneumatic cylinders has a pump mechanism mounted on the exterior of the cylinder. This is a significant shortcoming because the external pump structure significantly increases the size of the cylinder and also detracts from the aesthetic appeal. Because of the bulkiness of these devices, in many applications, the external pump structure makes the pneumatic cylinder impractical for use due to spatial limitations. For these reasons, none of the proposed self-chargeable pneumatic cylinders has gained widespread acceptance.  
         SUMMARY OF THE INVENTION  
         [0008]    The preferred embodiments of the present invention provide a new and improved self-chargeable pneumatic cylinder that does not require an external pump. The preferred embodiments also provide a self-chargeable pneumatic cylinder that is compact in size and has a rugged construction that ensures high quality and durability. Another feature of the preferred embodiments is that the self-chargeable pneumatic cylinder is well-suited for use as a pneumatic spring whereby the stiffness of the spring can be easily adjusted using the charging mechanism. The preferred embodiments are adapted to be made of a lightweight material that is resistant to corrosion. The preferred embodiments also provide a self-chargeable pneumatic cylinder that is very reliable, convenient to use and inexpensive to manufacture.  
           [0009]    A significant feature of the self-chargeable pneumatic cylinder in accordance with the present invention is the location of the internal pump mechanism. The pump mechanism is substantially self-contained within the interior portion of the pneumatic cylinder and therefore does increase the overall dimensions of the device. In addition, because the pump mechanism is located internally, the components of the pump mechanism are well protected from damage.  
           [0010]    In accordance with one aspect of the present invention, a pneumatic cylinder is presented generally comprising a hollow cylinder body having a closed end and an open end and a working piston slidably disposed in the interior of the cylinder body. A hollow elongate shaft is coupled to the working piston and extends out of the cylinder body via the open end. In a novel feature of the preferred embodiments of the present invention, the hollow interior portion of the shaft contains a manual pump mechanism. The manual pump mechanism generally comprises a pumping piston slidably disposed in the interior of the shaft and a pumping rod coupled to the pumping piston. The pumping rod is extendable out of the shaft via the open end and a handgrip is provided at the free end thereof for facilitating actuation of the pumping piston.  
           [0011]    In another aspect of the present invention, the internal pump mechanism advantageously includes a check device disposed on the pumping piston. The check device comprises an annular slot formed in the periphery of the pumping piston and an O-ring disposed in the annular slot. The O-ring is in frictional engagement with the inner wall of the shaft at all times. Due to frictional forces, the O-ring is forced upward against the top of the annular slot as the pumping piston is retracted through the interior of the shaft. With the O-ring in this configuration, air is free to pass around the pumping piston into a pressure adding chamber. When the pumping piston is subsequently advanced back into the shaft, the O-ring presses against the bottom of the annular slot and forms a seal that prevents air from escaping the pressure adding chamber.  
           [0012]    In another aspect of the present invention, a one-way valve is advantageously provided that extends through the working piston. The one-way valve allows air to flow in one direction only from the pressures adding chamber into the pressure cylinder to charge the cylinder with air as the pumping piston is actuated.  
           [0013]    In another aspect of the present invention, the pneumatic cylinder is advantageously provided with a two-way valve disposed on the closed end of the cylinder body. The two-way valve provides an alternative means for rapidly charging the gas chamber in the cylinder. The two-way valve also provides a means to rapidly discharge the gas from the gas chamber to the atmosphere.  
           [0014]    In another aspect of the preferred embodiments of the present invention, the shaft can be fully advanced into the cylinder after discharging all the gas from the cylinder. This feature can be used to reduce the size of the device for compact storage or transportation.  
           [0015]    In another aspect of the present invention, the pneumatic cylinder is well adapted for use as a pneumatic spring in a pogo stick. The pressure in the gas chamber can be varied using the pump mechanism and/or the two-way valve to accommodate the body weight and skill level of the user. In this application, a buffer sleeve may be placed over the bottom end of the shaft to provide a foot for engagement with the ground during use. Because of the compact size of the pneumatic cylinder, the device is particularly well-suited for use with a pogo stick that is collapsible into a small volume.  
           [0016]    In yet another aspect of the present invention, the pneumatic cylinder is well adapted for use with exercise equipment. The cylinder can be used with a wide variety of exercise machines wherein a resistance force is desirable. In this application, the resistance force can be adjusted to suit the user&#39;s exercise needs by varying the pressure in the cylinder. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 shows a perspective view of a preferred embodiment of the self-chargeable pneumatic cylinder of the present invention.  
         [0018]    [0018]FIG. 2 shows an exploded view of the self-chargeable pneumatic cylinder of FIG. 1.  
         [0019]    [0019]FIG. 3 shows a sectional view of the self-chargeable pneumatic cylinder of FIG.  
         [0020]    [0020]FIG. 4 shows an enlarged sectional view of the pump mechanism of the self-chargeable pneumatic cylinder of FIG. 1.  
         [0021]    [0021]FIG. 4A shows the same view as FIG. 4 but with the O-ring forming a seal in the check device to prevent the escape of air from the pressure adding chamber.  
         [0022]    [0022]FIG. 5 shows a perspective view of the self-chargeable pneumatic cylinder of FIG. 1 incorporated into a collapsible pogo stick.  
         [0023]    [0023]FIG. 6 shows another perspective view of the collapsible pogo stick of FIG. 5 in a collapsed condition.  
         [0024]    [0024]FIG. 7 shows a perspective view of the self-chargeable pneumatic cylinder of FIG. 1 incorporated into an exercise machine.  
         [0025]    [0025]FIG. 8A shows an enlarged side view of the exercise machine of FIG. 7 illustrating the self-chargeable pneumatic cylinder with a bar connected to the shaft.  
         [0026]    [0026]FIG. 8B shows another enlarged side view of the exercise machine of FIG. 7 whereby the pump rod is extended from the shaft for adjusting the resistance. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]    FIGS.  1 - 3  illustrate a preferred embodiment of a self-chargeable pneumatic cylinder  10  in accordance with the present invention. The self-chargeable pneumatic cylinder  10  includes, generally, a hollow cylinder body  20 , a working piston  30 , a hollow elongate shaft  40 , a one-way valve  50 , a pumping piston  60 , a check device  70 , and a pumping rod  80 .  
         [0028]    The cylinder body  20  comprises a cylindrical tube  21 , a top cover  22  for closing the top end of the cylindrical tube  21 , and an end member  23  fastened to the bottom end of the cylindrical tube  21 . A washer  26  is provided between the top end of the cylindrical tube  21  and the top cover  22  to ensure an airtight seal is formed therebetween. The interior of the cylinder body  20  defines a gas chamber  25  in the region between the top cover  22  and the working piston  30 . A two-way air valve  24  is disposed on the top cover  22  for selectively providing communication between the atmosphere and the gas chamber  25 .  
         [0029]    The working piston  30  is slidably disposed in the interior of the cylindrical tube  21 . The periphery of the piston  30  is provided with two annular slots  31  for respectively accommodating two piston rings  32 . Each of the piston rings  32  is provided with a pliable lip portion  321  on the outer edge as shown in FIG. 3. When the working piston  30  is moved inward or outward in relation to the cylindrical tube  21 , the piston rings  32  serve to provide an airtight seal between the working piston  30  and the inner wall of the cylindrical tube  21 .  
         [0030]    The hollow elongate shaft  40  is coupled at the top end to the working piston  30 . A washer  41  is provided between the top end of the shaft  40  and the working piston  30  to ensure that an airtight seal is formed therebetween. The end member  23  is provided at the bottom end of the cylindrical tube  21  and is formed with an opening  231  through which the shaft  40  extends outward therefrom. Three gas slots  232  extend axially along the opening  231  to allow atmospheric air to enter or exit the cylindrical tube  21  in the region behind the working piston  30 . The end member  23  and the working piston  30  are provided therebetween with two buffer rings  28  made of a resilient material. The buffer rings  28  provide a cushion to protect the components and reduce the noise that is produced when the working piston  30  contacts the end member  23 .  
         [0031]    In a novel feature of the preferred embodiments of this invention, a manual pump  59  is substantially contained within the hollow interior portion of the shaft  40 . The manual pump  59  generally comprises the pumping piston  60 , the pumping rod  80 , and the check device  70 . The manual pump  59  enables the user to charge the cylinder body  20  without using an external source of pressurized gas. Because the mechanism of the manual pump  59  is substantially contained within the shaft  40 , the overall size of the pneumatic cylinder is not increased by the pump structure.  
         [0032]    With reference now to FIG. 4, the details of the manual pump  59  are shown in greater detail. The pumping piston  60  is disposed in the interior of the shaft  40  such that a pressure adding chamber  61  is formed between the bottom end of the working piston  30  and the top end of the pumping piston  60 . The one-way valve  50  extends through the working piston  30  for allowing gas to enter the gas chamber  25  from the pressure adding chamber  61  while the manual pump is being actuated. The one-way valve  50  only allows gas to flow into the gas chamber  25  when the gas pressure in the pressure adding chamber  61  exceeds the gas pressure in the gas chamber  25 .  
         [0033]    The check device  70  on the pumping piston  60  comprises an annular slot  71  disposed on the peripheral edge of the pumping piston  60 , two indentations  73  providing communication between the annular slot  71  and the pressure adding chamber  61 , and an O-ring  74  disposed in the annular slot  71 . The inner edge of the annular slot  71  is slanted to form a narrow gap between the inner edge and the inner wall of the shaft  40  at the bottom of the annular slot  71 . When the O-ring  74  is pressed against the top of the annular slot  71 , gas is free to enter the pressure adding chamber  61 . Specifically, gas passes into the pressure adding chamber  61  via the interstice located between the pumping piston  60  and the shaft  40 , as well as the interstice located between the annular slot  71  and the O-ring  74 , and the indentations  73 , as indicated by arrows in FIG. 4. When the O-ring  74  is pressed against the bottom of the annular slot  71 , the O-ring  74  blocks the interstice between the pumping piston  60  and the shaft  40 . In this position, the O-ring forms a seal to prevent the escape of gas from the pressure adding chamber  61  as shown in FIG. 4A.  
         [0034]    It will be appreciated that the check device  70  just described is a versatile apparatus that can also be used for numerous other applications in the field of pneumatic pump technology. While the check device  70  is the preferred embodiment, other structures capable of bringing about an effect similar to that of the check device  70  are intended to be included within the scope of the present invention.  
         [0035]    Referring again to FIG. 3, the top end of the pumping rod  80  is coupled to the pumping piston  60 . The pumping rod  80  is provided at the bottom end with a base portion  81 . As shown in FIG. 3, a buffer sleeve  92  may be used to cover the base portion  81 , in which case the buffer sleeve  92  is used as a handgrip. The buffer sleeve  92  is secured to the base portion  81  by a bolt  82  that extends through the buffer sleeve  92  into the base portion  81 . The base portion  81  is also provided with a retaining projection  94  that extends through a retaining hole  96  in the shaft  40  to secure the base portion  81  to the shaft  40 . The retaining projection  94  is biased outward by a spring  98  housed within a cavity in the base portion  81 .  
         [0036]    In one particular application, the self-chargeable pneumatic cylinder  10  of the present invention is incorporated into a pogo stick  90  as illustrated in FIG. 5. When used with a pogo stick  90 , the self-chargeable pneumatic cylinder  10  provides a pneumatic spring of variable stiffness. The self-chargeable feature of the pneumatic cylinder  10  advantageously allows the spring stiffness to be adjusted to accommodate users of different body weights. Because the pump mechanism is contained within the shaft  40 , the stiffness of the pneumatic spring can be increased without using an external pump. Because the pneumatic spring involves very few moving parts, frictional forces are minimized and the pneumatic spring provides a very smooth and enhanced jumping motion. When the pneumatic spring is used with a pogo stick  90 , the shaft  40  is preferably provided at the bottom end with the buffer sleeve  92 . The buffer sleeve  92  cushions the impact during use and protects the bottom end of the shaft  40  from damage.  
         [0037]    Because the pump mechanism of the present invention is contained within the shaft  40  and the shaft can be withdrawn into the cylinder body  20 , the pneumatic cylinder  10  of the present invention is very compact in size. Therefore, the pneumatic cylinder  10  is ideally suited for an application such as with a pogo stick  90  that is manufactured to be collapsible for compact storage and transportation as shown in FIG. 6. Further details as to a pogo stick of this type are disclosed in our co-pending application entitled “Collapsible Pogo Stick” (Attorney Docket No. RAZOR.001A), Serial No. ______, filed on the same date as the present application. The disclosure of this reference is herein incorporated in its entirety by reference thereto.  
         [0038]    The operation and use of the self-chargeable pneumatic cylinder as used in a collapsible pogo stick will now be described with reference to FIGS.  1 - 6 . The pneumatic cylinder  10  is prepared for use by releasing the pump rod  80  from the shaft  40  by pushing the retaining projection  94  out of the retaining hole  96 . The user grips the buffer sleeve  92  at the base of the pump rod  80  and pulls the buffer sleeve outward from the shaft  40  thereby causing the pumping piston  60  to retract axially within the interior of the shaft  40 . The outward movement of the pumping piston  60  causes a frictional force to be exerted on the O-ring  74  by the inner edge of the shaft  40  thereby causing the O-ring  74  to press against the top wall of the annular slot  71 . With the O-ring in this position, the pressure adding chamber  61  is in communication with the atmosphere. Therefore, during the retraction of the pumping piston  60 , the gas under the pumping piston  60  is sucked into the pressure adding chamber  61  through the check device  70 .  
         [0039]    Next, the pumping piston  60  is advanced into the shaft  40  by pushing the pumping rod  80  back into the shaft  40  to decrease the internal volume of the pressure adding chamber  61  and thereby increase the gas pressure. The advancement of the pumping piston  60  causes a frictional force to be exerted on the O-ring  74  by the inner wall of the shaft  40  thereby causing the O-ring  74  to press against the bottom end of the annular slot  71 . With the O-ring in this position, the check device  70  forms a seal in the pumping piston  60  that prevents the gas in the pressure adding chamber  61  from escaping during advancement of the pumping piston  60 . When the gas pressure in the pressure adding chamber  61  exceeds the gas pressure in the gas chamber  25 , gas flows from the pressure adding chamber  61  to the gas chamber  25  in the cylinder body  20  via the one-way valve  50 . The pumping rod  80  is reciprocally actuated in this manner until the desired pressure in the gas chamber  25  is attained. After the pneumatic cylinder  10  has been charged as described above, the pumping rod  80  is locked back into the shaft  40  and the pneumatic cylinder  10  is ready for use.  
         [0040]    The collapsible pogo stick is prepared for use by attaching the grips to the middle tube, pivoting the plates downward to form a footrest, and extending the handlebar upward to the desired height to resemble the pogo stick illustrated shown in FIG. 5. When the user jumps on the pogo stick, the buffer sleeve  92  at the base of the shaft  40  strikes the ground with each downward cycle thereby forcing shaft  40  and working piston  30  upward into the cylinder body  20 . The movement of the working piston  30  within the cylinder body  20  compresses the gas in the gas chamber  25 , thereby resulting in a reaction force which serves as a spring to propel the working piston  30  and shaft  40  back downward from the cylinder body  20 .  
         [0041]    After use, the working piston  30  may be completely advanced into the cylinder body  20  by discharging all the gas from the gas chamber via the two-way valve  24 . With the working piston  30  completely advanced into the cylinder body  20 , the volume of the pneumatic cylinder  10  is minimized for compact storage and complements the collapsible features of the collapsible pogo stick.  
         [0042]    In another application, the self-chargeable pneumatic cylinder  10  of the present invention can be advantageously incorporated into an exercise machine  100  as illustrated in the example shown in FIGS.  7 - 8 B. In this particular application, the pneumatic cylinder  10  provides a resistance force for building muscle strength in the arms. The pneumatic cylinder may also be used to provide adjustable resistance in other exercise machines, such as, for example, an abdominal exerciser or a leg press. The self-chargeable feature described above allows the user to adjust the pressure in the cylinder, which in turn adjusts the resistance force to suit the user&#39;s needs during exercise. Using the pneumatic cylinder  10  of the present invention eliminates the need for heavy weights and elastic members that can fatigue or break.  
         [0043]    Referring still to the example illustrated in FIGS.  7 - 8 B, a bar  102  is attached to the bottom end of the shaft  40  of the pneumatic cylinder  10  by welding, bolts or other suitable means. The user sits or lies on the bench  104  and grips the bar  102 . The user pushes upward on the bar  102  to force the shaft  40  into the cylinder body  20 F. FIG. 8A shows an enlarged view of the pneumatic cylinder  10  used in this application. The base portion  81  includes a retaining projection  94  that fits into a retaining hole  96  in the shaft  40  for securing the base portion  81  to the shaft  40 . As shown in FIG. 8B, the base portion  81  can be released from the shaft  40  and extended downward for actuating the pumping rod  80  to increase the pressure in the cylinder  40 . A valve (not shown) is provided on the cylinder for releasing gas from the cylinder  20  to decrease the resistance force.  
         [0044]    In each of the embodiments described above, a significant feature of the present invention is the rugged quality of the components and the solid construction of the pneumatic cylinder. In the preferred embodiments, the primary components of the self-chargeable pneumatic cylinder are formed of a lightweight, non-rusting aluminum alloy, such as  6061 . Because aluminum is lightweight and the components are generally hollow in construction, the self-chargeable pneumatic cylinder has great strength yet can be easily transported by the user. Aluminum is resistant to corrosion and therefore the self-chargeable pneumatic cylinder can be left outdoors for extended periods without rusting or diminishing in aesthetic value. Aluminum is also very durable and therefore the self-chargeable pneumatic cylinder can withstand impacts without incurring significant damage and will have a very long design life.  
         [0045]    From the foregoing, it will be appreciated that the present invention is adaptable for use in a wide range of applications in the field of pneumatic and hydraulic cylinder technology. While particular forms of the invention have been illustrated and described, it will also be apparent that various additional modifications can be made without departing from the spirit and scope of the invention.