Abstract:
A bicycle air pump includes a cylinder adapted to be secured to the bicycle frame having a cylinder bore within which a piston reciprocates, a crank shaft rotatably supported on the cylinder and drivingly coupled to the piston by means of a connecting rod and a driving mechanism for coupling the crank shaft to the bicycle chain to be driven thereby so that when the bicycle pedals are actuated to drive the bicycle chain, the bicycle chain forces the crank shaft to rotate and thus making the piston reciprocate within the cylinder bore to pump air through an outlet of the cylinder.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to an air pump and in particular to an air pump structure which allows the pump to be fixed to a bicycle frame and driven by the bicycle chain so that the bicycle rider may be able to fix a tire pressure problem in any time and at any place. 
     BACKGROUND OF THE INVENTION 
     Bicycles have been widely used in transportation and exercise. The tire pressure of the bicycle is an important factor that affects the comfort of riding bicycle. The tire pressure has to be maintained at a predetermined level in order to get a comfortable riding experience. Furthermore, sometimes, the bicycle tires may be damaged and a flat tire occurs. Thus, an air pump is of importance for a bicycle rider. 
     Conventional air pumps, such as hand operating air pump indicated at  10  in FIG. 8 of the attached drawings or foot operating air pump indicated at  20  in FIG. 9, are not designed to be carried with the bicycle so that when the tire pressure gets lower than the predetermined level or a flat tire occurs, the bicycle rider is not able to obtain instant and handy means to fix the tire pressure problem. 
     Thus, it is desirable to provide a bicycle air pump which is mounted on the bicycle and driven by the operation of the bicycle so as to provide a handy way for supply air to the bicycle tire. 
     SUMMARY OF THE INVENTION 
     Therefor, an object of the present invention is to provide an air pump which is suitable to be mounted on the bicycle to be carried thereby so as to provide a handy air supply to the bicycle tire. 
     Another object of the present invention is to provide an air pump which is mounted to the bicycle frame to be carried thereby and which is driven by the operation of the bicycle so as to provide an efficient way of supplying air to the bicycle tire. 
     To achieve the above objects, in accordance with the present invention, there is provided a bicycle air pump comprising a cylinder adapted to be secured to the bicycle frame, having a cylinder bore within which a piston reciprocates, a crank shaft rotatably supported on the cylinder and drivingly coupled to the piston by means of a connecting rod and means for coupling the crank shaft to the bicycle chain to be driven thereby so that when the bicycle pedals are actuated to drive the bicycle chain, the bicycle chain forces the crank shaft to rotate and thus making the piston reciprocate within the cylinder bore to pump air through an outlet of the cylinder. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be better understood from the following description of a preferred embodiment thereof, with reference to the attached drawings, wherein: 
     FIG. 1 is a perspective view showing a bicycle air pump constructed in accordance with the present invention; 
     FIG. 2 is an exploded perspective view of the bicycle air pump in accordance with the present invention 
     FIG. 3 is a cross-sectional view of the bicycle air pump of the present invention with the chain wheel of the bicycle air pump at the stowed position; 
     FIG. 4 is a cross-sectional view similar to FIG. 3, but showing the chain wheel of the bicycle air pump at the working position; 
     FIG. 5 is a schematic side elevational view showing the bicycle air pump of the present invention mounted to the frame of a bicycle; 
     FIG. 6 is a schematic side elevational view similar to FIG. 5, but showing the chain wheel of the bicycle air pump of the present invention engaged and driven by the bicycle chain of the bicycle; 
     FIG. 7 is a schematic side elevational view similar to FIG. 6, but showing a flexible tube is used to connect the outlet of the bicycle air pump to a bicycle tire; and 
     FIGS. 8 and 9 are perspective views of two conventional air pump structures. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the drawings and in particular to FIGS. 1-3, wherein a bicycle air pump constructed in accordance with the present invention, generally designated with reference numeral  1 , is shown, the bicycle air pump  1  comprises a cylinder  10  having a cylinder bore  11  formed therein within which a piston  2  is movably received. The cylinder  10  is adapted to be fixed to a bicycle frame (see FIGS. 5-7) with any known means, such as bolts. A crank shaft  5 , which has a hollow portion, is coupled to the piston  2  by means of a connecting rod  3  to drive the piston  2  reciprocating inside the cylinder bore  11 . A driving shaft  6  telescopically and axially movably received within the hollow crank shaft  5  and rotatably fixed thereto to be rotatable in unison therewith for driving the crank shaft  5 . The driving shaft  6  has a chain wheel  7  fixed thereto, which chain wheel  7  is adapted to be coupled to and driven by a chain  40  of the bicycle (see FIGS. 5-7) so that when a rider (not shown) actuates pedals  30  of the bicycle to drive the bicycle chain  40 , the piston  2  is forced to reciprocate within the cylinder  10  by means of the mechanical coupling provided by the chain wheel  7 , the driving shaft  6 , the crank shaft  5  and the connecting rod  3  and thus air is pumped and supplied through an outlet  12  of the cylinder  10 . 
     In accordance with the present invention, the crank shaft  5  comprises an elongated shaft body  50  extending through and rotatably supported within a hole  15  formed on the cylinder  10 . Preferably the cylinder  10  is provided with a side wall plate  16  having an extension beyond a lower end of the cylinder  12  with the hole  15  formed on the lower extension of the side wall plate  16 . The crank shaft  5  also comprises an arm  4  which is fixed to a first end of the shaft body  50 . The arm  4  has a coupling pin  41  fixed thereto and extending therefrom in a direction substantially parallel with the elongated shaft body  50  to be rotatably received within a corresponding hole  30  formed on the connecting rod  3  so as to form a rotatable or pivotal joint therebetween. 
     In the embodiment illustrated, the first end of the elongated shaft body  50  is provided with a reduced diameter so as to define a shoulder. The arm  4  is provided with a hole  42  corresponding to and fit over the first end of the shaft body  50  and retained thereon by the shoulder of the shaft body  50 . Preferably, the first end of the shaft body  50  is provided with a threading  54  to which a nut  55  is engaged to secure the arm  4  to the elongated shaft body  50  so as to force the coupling pin  41  to rotate about the elongated shaft body  50  when the shaft body  50  rotates. 
     The elongated shaft body  50  is also provided with a reduced second end which defines a shoulder placed against the hole  15  of the cylinder  10  and an external threading  52  on the second end to which a nut  56  is engaged to secure the elongated shaft body  50  to the side wall plate  16  of the cylinder  10  in such a way to allow the shaft body  50  to be rotatable with respect to the cylinder  10 . In this respect, it may be desired to have bearing means (not shown) arranged between the hole  15  and the shaft body  50 . 
     The connecting rod  3 , besides the hole  30 , has a second hole  31  through which a pin  22  extends. The pin  22  also extends through holes  23  formed on support plates  21  fixed to the piston  2  so as to form a rotatable or pivotal joint between the piston  2  and the connecting rod  3 . With such an arrangement, when the crank shaft  5  rotates, the piston  2  is driven to reciprocate within the cylinder bore  11 . 
     The elongated shaft body  50  of the crank shaft  5  has a central axial bore  51  into which the driving shaft  6  is axially slidably received. The driving shaft  6  is provided with an elongated, axially-extending slot  61 , serving as a keyway. The elongated shaft body  50  is provided with a radially extending hole  57  into which a pin  53  is received. The pin  53  extends through the hole  57  and partially received within the slot  61  of the driving shaft  6  to serve as a key so that by means of the key-keyway engagement of the pin  53  and the slot  61  of the driving shaft  6 , the rotation of the driving shaft  6  is transmitted to the crank shaft  5 . 
     In addition to the driving connection provided by the engagement between pin  53  and the slot  61  of the driving shaft  6 , the slot  61  and the pin  53  also serve to prevent the driving shaft  6  from sliding off the central bore  51  of the elongated shaft body  50  of the crank shaft  5 . This is done by means of the stopping engagement between the pin  53  and axial ends of the driving shaft  6 . 
     The driving shaft  6  has an axial length so as to have an end thereof extending out of the crank shaft  5  and the chain wheel  7  is secured to the end of the driving shaft  6 . This may be done by forming threading  62  on the end of the driving shaft  6  with a nut  8  engaged thereto to secure the chain wheel  7  to the driving shaft  6  in such a way to have the driving shaft  6  and the chain wheel  7  rotatable in unison with each other. 
     The elongated slot  61  allows the driving shaft  6  to be axially movable relative to the crank shaft  5  so that the chain wheel  7  that is secured to the driving shaft  6  is moveable relative to the side wall plate  16  of the cylinder  10  between a stowed position (see FIG. 3) and a working position (see FIG.  4 ). 
     To shield the chain wheel  7  in the stowed position, a cylindrical shielding member  13  is fixed to the side wall plate  16  of the cylinder  10  and is arranged to be substantially co-axial with the hole  15 . The cylindrical member  13  has a size that is sufficient to shield the chain wheel  7  in the stowed position, but allows the chain wheel  7  to be exposed in the working position. 
     If desired, a pressure gauge  9  may be attached to the cylinder and in fluid communication with the outlet  12  of the cylinder  10  to indicate the pressures of the pumped air supplied by the air pump  1  of the present invention. 
     A cover member  14  may be provided to cover and protect the crank shaft  5  and the connecting rod  3 . 
     As shown in FIGS. 5-7, the air pump  1  of the present invention may be fixed to a suitable position on the bicycle frame so as to allow the chain wheel  7  (at the working position) to be engaged by the chain  40  by manually deflecting the chain  40  (FIGS. 6 and 7) and thus when the rider depresses the pedals  30 , the chain  40  is driven to rotate the chain wheel  7  which in turn drives the piston  2  to reciprocate within the cylinder bore  11  to pump air through the outlet  12 . A flexible tube  60  (see FIG. 7) may be used to connect between the outlet  12  of the air pump  1  and for example a tire  50  to supply the pumped air into the tire  50 . Of course, the flexible tube  60  may be used to connect the air pump  1  to any desired destination to supply pressurized air thereto. 
     Preferably, the cover  14  is made in such a way to provide an interior space therein which space is sufficient to accommodate the flexible tube  60  therein. 
     Although the a preferred embodiment has been described to illustrate the present invention, it is apparent that changes and modifications in the specifically described embodiment can be carried out without departing from the scope of the invention which is intended to be limited only by the appended claims.