Abstract:
An improved air pump comprises at least two parallel cylinder chambers communicating via two channels with a receiving space in which an air valve connecting device is disposed for injecting high pressure air into an object to be inflated. A pressure releasing member is disposed between the channels and the receiving space for regulating the pace of pumping the air into the object. When the air pressure inside the object is low, the pumping of the air into the object is done rapidly. When the air pressure inside the object has reached a high level, the pumping of the air into the object is done by only one cylinder chamber of the air pump.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to an air pump, and more particularly to an air pump provided with means for improving the pumping efficiency and effect. 
     BACKGROUND OF THE INVENTION 
     The efficiency of a conventional air pump of the early model is rather limited in that the pumping of air is effected in a one-way manner that the air is driven into something, such as a tire, only when the piston of the pump is driven to move in a specific direction. However, such a conventional air pump was improved to an extent that the pumping of air could take place in a two-way fashion when the piston of the pump was caused to make a reciprocating motion. In order to improve further the efficiency and the effect of the conventional air pumps, the cylinders of the air pumps were diametrically enlarged to allow a greater amount of air to be driven into a tire and the like. However, such an improvement as mentioned above is also limited in that the pumping effect and the pumping efficiency are both undermined because the cross-sectional area of the pump cylinder is inversely proportional to the pressure, thereby causing a person to encounter with a difficulty in pumping even when the tire pressure has not reached a required level. 
     SUMMARY OF THE INVENTION 
     It is therefore the primary objective of the present invention to provide an improved air pump, which overcomes the shortcomings of the conventional air pumps described above. 
     The foregoing objective of the present invention is attained and described by embodiments which are described hereinafter in conjunction with the drawings provided herewith. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a longitudinal sectional view of a preferred embodiment of the present invention. 
     FIGS. 2 and 3 show schematic views of the pumping of a first preferred embodiment as shown in FIG. 1. 
     FIG. 4 is a schematic view showing that only one cylinder chamber of the pump of the present invention is at work at the time when the pressure is high. 
     FIG. 5 shows a sectional schematic view of a second preferred embodiment in action, according to the present invention. 
     FIG. 6 is a schematic view showing that only one cylinder chamber of the second preferred embodiment as shown in FIG. 5 is at work. 
     FIG. 7 shows a side elevational schematic view of a third preferred embodiment of the present invention. 
     FIG. 8 shows a sectional view of a portion taken along the line 8--8 as shown in FIG. 7. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 and 2, the first preferred embodiment of the present invention comprises a first cylinder chamber 12, a second cylinder chamber 14, a receiving space 16, a first channel 18 and a second channel 20 which are in communication with the first cylinder chamber 12, the second cylinder chamber 14 and the receiving space 16. The cylinder chambers 12, 14 and the channels 18, 20 are disposed in a cylinder 10 such that they are parallel to one another. The two cylinder chambers 12 and 14 have respectively a free end that is fitted into a cover 15. The receiving space 16 is disposed in a head 22, which is made separately or integrally with the cylinder 10. The receiving space 16 passes through the top and the bottom ends of the head 22. The channels 18 and 20 are connected respectively with the circumference of the receiving space 16. The head 22 is provided on the edge of the top end thereof with a pair of lugs 24. The head 22 is further provided at the bottom thereof with a pressing member 26. 
     Two pistons 30 are disposed respectively in the two cylinder chambers 12 and 14 such that the pistons 30 divide the cylinder chamber into a first air pressure chamber 32 and a second air pressure chamber 34. Each of the two pistons 30 is provided in the circumferential surface thereof with an annular groove 36 for disposing therein a leakproof ring 40. The annular groove 36 is provided with a cut 38. 
     Two piston rods 42 are disposed in the two cylinder chambers 12 and 14 and connected with the two pistons 30. 
     An air valve connecting device comprising: 
     a tightening member 48 of a plastic material and disposed under the receiving space 16; 
     a supporting member 54 provided centrally with a valve chamber 58 and at the top end thereof with a first air inlet 60 and a second air inlet 64, which are in communication with the valve chamber 58 having a bottom wall provided with a predetermined number of projections 66; and 
     a valve piece 68 disposed in the valve chamber 58. 
     The supporting member 54 is disposed in the receiving space 16 such that the supporting member 54 is attached to the tightening member 48 and that the supporting portion 56 of the supporting member 54 is received in the inner holes 50 and 52 of the tightening member 48. The second air inlet 64 is corresponding in location to the first channel 18. 
     A pressure releasing member 70 is disposed between the receiving space 16 and the second channel 20 and is composed of the component parts described hereinafter. 
     A position limiting piece 72 is of an elastic element having an elasticity coefficient greater than that of the tightening member 48. The position limiting member 72 is disposed in the receiving space 16 such that the position limiting member 72 makes contact with the supporting member 54. 
     A pressure releasing piece 74 of columnar construction and having on the circumferential surface thereof two annular grooves in which a first leakproof member 78 and a second leakproof member 80 are disposed. The pressure releasing piece 74 is disposed in the receiving space 16 such that the pressure releasing piece 74 is urged by the position limiting piece 72. There is a gap between the bottom of the pressure releasing piece 74 and the top of the position limiting piece 72 for air to flow therethrough. The two leakproof elements 78 and 80 are corresponding in location to the outlet of the second channel 20. 
     A pressure adjusting piece 82 has one end provided with a first locating portion 84 and a second locating portion 86, which have respectively a slanted surface and which intersect at a predetermined angle. The pressure adjusting piece 82 is pivoted at that one end thereof to the lug 24 of the head 22 and is therefore capable of rotating on the pivoting point serving as a fulcrum. The distance between the second locating portion 86 and the pivoting point is greater than the distance between the first locating portion 84 and the pivoting point. 
     In operation, the tightening member 48 of the air pump of the present invention is fitted over the air valve 92 of a tire 90, as shown in FIG. 2. The pressing member 26 is so rotated as to cause the tightening member 48 to deform. The pressure adjusting piece 82 is pushed upwards to cause the pressure releasing piece 74, the position limiting piece 72 and the supporting member 54 to move downwards, thereby bringing about the deformation of the tightening member 48 so as to seal off the air valve 92. In the meantime, the first leakproof element 78 is corresponding in location to the outlet of the second channel 20 while the second leakproof element 80 is located between the second channel 20 and the top edge of the receiving space 16 so as to keep the receiving space 16 airtight. The two pistons 30 can be caused respectively to compress the first air pressure chambers 32 of the two cylinder chambers 12 and 14 by exerting a pressure on the hand grip 44 in a direction indicated by an arrow as shown in FIG. 2. As a result, the high pressure air is caused to flow to the receiving space 16 via the two channels 18 and 20. As the piston 30 is caused to compress the first air pressure chamber 32, the atmospheric air is injected into the second air pressure chamber 34 via the gap located between the piston rod 42 and the cover 15. The high pressure air is then caused to flow from the receiving space 16 to the valve chamber 58 via the second air inlet 64 of the supporting member 54. The high pressure air is subsequently allowed to enter the axial hole 62 of the supporting member 54 via the gap located between the valve piece 68 and the projection 66. It is the axial hole 62 through which the high pressure air is injected into the tire 90 via the air valve 92 of the tire 90. Similarly, the high pressure air in the second cylinder chamber 14 is caused to flow into the receiving space 16. Thereafter, the high pressure air is allowed to flow through the gap located between the pressure releasing member 74 and the position limiting member 72 before entering the valve chamber 58 via the first air inlet 60 of the supporting member 54. The high pressure air in the valve chamber 58 is finally injected into the tire 90 via the air valve 92. The receiving space 16 is airtight by virtue of the second leakproof element 80. As a result, no high pressure air is leaked out at the time when the operation of pumping the tire 90 by the two cylinder chambers 12 and 14 is under way. 
     As shown in FIG. 3, when the piston 30 has reached the dead center of its forward movement and begun to move backwards, the air pressure in the second air pressure chamber 34 causes the portion of the leakproof ring 40, which is corresponding in location to the cut 38, to deform so as to allow the high pressure air to enter the first air pressure chamber 32. The piston 30 is no longer compressing the air to pump the air into the tire 90. As a result, the valve piece 68 is pushed upwards by the air pressure of the tire 90 to become attached to the top wall of the valve chamber 58, thereby sealing off the air inlets 60 and 64 to prevent the air in the tire 90 from leaking out. 
     As the piston 30 has reached the dead center of its backward movement, the action of pumping the tire 90 is resumed. The valve piece 68 is caused to move downwards so as to permit the passage of the air. 
     The air pump with two cylinder chambers is very efficient in pumping the air into a tire. As the air pressure in the tire has reached a certain level, it becomes more difficult to pump additional air into the tire. Such a difficulty can be overcome by using only one of the two cylinder chambers 12 and 14 in the pumping operation. As shown in FIG. 4, the pressure adjusting member 82 is pushed upwards so as to cause the second locating portion 86 to press the pressure releasing member 74 downwards. The tightening member 48 continues to seal off the air valve of the tire by virtue of the deformation of the position limiting member 72. Upon completion of the downward movement of the pressure releasing member 74, the first leakproof element 78 is located under the second channel 20 to seal off the wall of the receiving space 16. As a result, the passageway located between the first channel 18 and the second channel 20 is obstructed. In the meantime, the second leakproof element is corresponding in location to the outlet of the second channel 20 and is no longer sealing off the circumferential surface of the receiving space 16, thereby forming a passageway located between the second channel 20, the pressure releasing member 74 and the receiving space 16. As the piston 30 is caused to compress the air in the cylinder chambers 12 and 14, the first cylinder chamber 12 generates a high pressure air, which is subsequently pumped into the tire. In the meantime, the air in the first air pressure chamber 32 of the second cylinder chamber 14 is caused to move by the piston 30 to be released to the atmosphere via the gap located between the second channel 20, the pressure releasing member 74 and the wall of the receiving space 16. In other words, the action of pumping the tire is carried out by the first cylinder chamber 12 only. The pumping action area of the piston 30 is therefore reduced substantially so that additional air can be pumped easily into the tire which has already been inflated previously to a certain level. 
     As shown in FIG. 5, the air pump of the second preferred embodiment of the present invention is different from that of the first preferred embodiment of the present invention in that the former has a piston 30 which is provided radially with an air hole 35, which is in turn provided in two sides thereof with leakproof rings 40 and 41. In addition, the piston rod 42 of the second preferred embodiment of the present invention is connected between the channels 18, 20 and the piston 30. The high pressure air formed by the compression brought about by the reciprocating motion of the piston 30 in either the first air pressure chamber 32 or the second air pressure chamber 34 is allowed to flow to the channels 18 and 20 via the air hole 35 and the duct 43 of the piston rod 42. The atmospheric air is injected into the second air pressure chamber 34 via a one-way valve (not shown in the drawings) located between both ends of the cylinder chambers 12, 14 and the cover 15. 
     The air pump of the second preferred embodiment, as shown in FIG. 5, comprises the component parts described hereinafter. 
     A receiving space 16 is disposed in such a manner that it is put through the bottom end of the head 22. The receiving space 16 is used to house the tightening member 48 and the supporting member 54, which are located by means of the pressing member 26. 
     The first channel 18 is connected with the receiving space 16 and is corresponding in location to the supporting member 54. The second channel 20 is not in communication with the receiving space 16. The two channels 18 and 20 are in communication with each other by means of an air duct 21 having one end connected with the first channel 18 and having another end connected with the second channel 20 such that another end passes through and beyond the head 22. 
     The pressure releasing member 70 comprises the pressure releasing member 74 of rod-shaped construction and the pressure adjusting member 82. The pressure releasing member 74 is provided with the first and the second leakproof elements 78 and 80. The pressure releasing member 74 is disposed in the air duct 21 such that the two leakproof elements 78 and 80 can seal off the air duct 21. The pressure adjusting member 82 is provided at one end thereof with a first locating portion 84 and a second locating portion 86. The pressure adjusting member 82 is pivoted at that one end mentioned above to the top end of the head 22. The body of the pressure adjusting member 82 is pivoted to the protruded end of the pressure releasing member 74 for actuating the pressure releasing member 74. 
     The two leakproof rings 40 and 41 disposed on the piston 30 work in a one-way manner that they prevent the air in the duct 43 and the air hole from entering the cylinder chamber. As a result, the supporting member 54 is not provided with the valve chamber 58 and the valve piece 68. 
     In operation, the pressure adjusting member 82 is moved to cause the first locating portion 84 to be retained securely. The pressure releasing member 74 is actuated by the pressure adjusting member 82 to move upwards. In the meantime, the second leakproof element 80 is located at the second channel 20 to seal off the air duct 21 so as to isolate the second channel 20. The first leakproof element 78 is corresponding in location to the outlet of the second channel 20. The high pressure air formed by the compression in the first cylinder chamber 12 is injected into the tire via the first channel 18 and the receiving space 16. The high pressure air formed by the compression in the second cylinder chamber 14 is also injected into the tire via the air duct 21 and the first channel 18. After the tire pressure has reached a certain level, the pumping of the air into the tire may be carried out by only one cylinder chamber. The pumping of the air by one cylinder chamber is initiated by pulling the pressure adjusting member 82 to retain the second locating portion 86. The pressure releasing member 74 is actuated to move downwards, as shown in FIG. 6, to cause the first leakproof element 78 to seal off the air duct 21 so as to obstruct the passageway between the first channel 18 and the second channel 20. In the meantime, the second leakproof element is located at the outlet of the second channel 20. The first cylinder chamber 12 remains effective in pumping the air into the tire. The high pressure air formed by the compression in the second cylinder chamber 14 is released to the outside of the air pump via the air duct 21. The tire is therefore inflated to have a greater air pressure by means of only one cylinder chamber. 
     The third preferred embodiment of the present invention is shown in FIGS. 7 and 8 in which the definitions of the reference numerals are similar to those of the first preferred embodiment of the present invention. The third preferred embodiment is different from the first preferred embodiment in that the head 22 or one side of the circumferential surface of the cylinder body of the third preferred embodiment is provided with a slot 23 in communication with the air duct 21. The slot 23 is provided with a first locating portion 231 and a second locating portion 232. The portion of the pressure releasing member 74, which is located between the two leakproof elements 78 and 80, is provided radially with a protruded portion 75 which is put through and beyond the slot 23 when the pressure releasing member 74 is disposed in the air duct 21. A tapered leakproof body 96 of a soft material is fitted over the protruded portion 75 such that the tapered leakproof body 96 seals off the circumferential surface of the head 22 by means of the portion thereof having a greater diameter. The work of sealing off the head 22 with the tapered leakproof body 96 is done by means of a high frequency device. The portion of the leakproof body 96, which has a smaller diameter, is fitted over the protruded portion 75 in an airtight manner, as shown in FIG. 8, so as to ensure that the slot 23 is airtight. 
     The protruded portion 75 can be moved to locate between the first and the second locating portions 231 and 232. In the meantime, the pressure releasing member 74 is movable in both directions inside the air duct 21, thereby enabling the sealing positions of the two leakproof elements 78 and 80 to be altered so as to connect the first and the second channels 18 and 20 or to isolate the first and the second channels 18 and 20. As a result, the air pump of the present invention can be put into operation, with only one cylinder chamber working to pump the air into the tire or with both cylinder chambers working simultaneously to pump the air into the tire. 
     The embodiments of the present invention desribed above are to be regarded in all respects as merely illustrative and not restrictive. Accordingly, the present invention may be embodied in other specific forms without deviating from the spirit thereof. For example, the air pump of the present invention may be provided with three or more cylinder chambers. The present invention is therefore to be limited only by the scope of the following appended claims.