Abstract:
A dual-direction pump includes two cylinders arranged on opposite sides of a head portion and an inlet return-flow prevention device and a leakproof device mounted between the cylinder and the head portion for avoiding leakage at the juncture between the cylinder and the head portion or leakage induced by reverse flow in one of the cylinders in the case of a single-sided pumping operation in the other cylinder. The head portion has an outlet port to which an outlet return-flow prevention device is mounted. A knob is rotatably mounted to the outlet pot and a nut is fixed to the knob for selectively engaging an inflation valve to avert detachment. The outlet return-flow prevention device prevents reverse or return flow induced in the outlet port in order to reduce resistance caused thereby and enhances pumping efficiency.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a pump for inflating a bicycle tire or ball, and more particularly to a pump capable of preventing reverse airflow or air leakage. 
   2. The Prior Arts 
   U.S. Pat. No. 6,350,112 discloses a dual-direction pump comprising a head portion composed of two cylinders arranged on opposite sides of the head portion, and a connector mounted to the head portion for releasable connection with a valve of tire for inflation. 
   Since conventionally, the inflation connector is coupled to the head portion in a non-secured manner, it is liable to come off because of vibration or due to reasons whatsoever during inflating. Moreover, as there is no return-flow prevention device available in the head portion, both cylinders have to work simultaneously in order to prevent air from leaking through the other side. 
   SUMMARY OF THE INVENTION 
   A primary object of the present invention is to provide a dual-direction pump for eliminating the drawbacks of leakage through the other side during an inflation process. 
   Another object of the present invention is to provide a dual-direction pump for eliminating the problem of easy detachment of the coupling between the head portion and the inflation valve. 
   In order to realize the objects, a feature of the present invention comprises a return-flow prevention device, such as a check valve, mounted in each cylinder to avoid reverse flow and thus leakage of air in an inflation process. 
   A second feature of the present invention comprises a nut-carried knob at an outlet end of the pump so as to avoid potential detachment of the head portion from an inflation valve. 
   Basing on above concepts, two pumping cylinders are arranged on two opposite sides respectively at the head portion of pump, and an inlet return-flow prevention device as well as a leakproof device is mounted between each cylinder and the inlet of the head portion for avoiding leakage at the juncture between the cylinder and the head portion or through the other cylinder side in the case of single-side pumping operation. Also, the outlet end of the head portion is provided with an outlet return-flow prevention device and a knob. The knob is combined with a nut for releasably and effectively attaching to an inflation valve to avert detachment. The outlet return-flow prevention device prevents a reverse or return flow so as to reduce resistance caused thereby and enhances pumping efficiency. 
   The merits of the present invention is summarized as follows: 
   1. Compared with the prior arts, the present invention effectively eliminates leakage air on the other side when single-side inflation is performed. 
   2. The head portion of the air pump is securely attached to the inflation valve of for example a tire when the tire is inflated and undesired detachment of the pump from the tire is eliminated. 
   For more detailed information regarding advantages or features of the present invention, at least an example of preferred embodiment will be described below with reference to the annexed drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The related drawings in connection with the detailed description of the present invention to be made later are described briefly as follows, in which: 
       FIG. 1  is a cross-sectional view of a dual-direction pump constructed in accordance with the present invention; 
       FIG. 2  is a side elevational view of a portion of the dual-direction pump showing one of the cylinders and the head portion thereof; 
       FIG. 3  is an exploded view of  FIG. 2 ; 
       FIG. 4  is a cross-sectional view showing a return-flow prevention device arranged in an inlet between the head portion and the cylinder of the dual-direction pump of the present invention at an open condition; 
       FIG. 5  is similar to  FIG. 4  but showing the return-flow prevention device at a closed condition; 
       FIG. 6  is a cross-sectional view showing a return-flow prevention device arranged in an outlet end of the head portion of the dual-direction pump of the present invention at an open condition; and 
       FIG. 7  is similar to  FIG. 6  but showing the return-flow prevention device at a closed condition. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   With reference to the drawings and in particular to  FIG. 1 , a dual-direction pump constructed in accordance with the present invention comprises a head portion  1  having two inlets to each of which a cylinder  2  is mounted. In the embodiment illustrated, the inlets are arranged on opposite sides of the head portion  1  whereby the cylinders  2  are opposite to each other. Each cylinder  2  comprises a rod  22  drivingly coupled to a piston  23  movable in the cylinder  2 . A handgrip  24  is mounted to a free end of the rod  22  for manually and axially moving the piston  23  by the rod  22 . Air is the cylinder  2  is thus compressed and forced into the head portion  1 . 
   Also referring to  FIGS. 2 and 3 , the head portion  1  has two inlet ports  10  to which the cylinders  2  are respectively mounted. An inner threading  11  is formed on an inner wall (not labeled) of the inlet portion for engaging an outer threading  21  formed on an outside surface (not label) of the cylinder  2  thereby releasably attaching the cylinder  2  to the inlet port  10  of the head portion  1 . An inlet duct  12  is defined inside and in a center of the inlet port  10 . An inlet channel  13  is defined in the head portion  1  and is in communication with and extends from a bottom of the inlet duct  12  to an outlet channel  14 . A plurality of radially extending grooves  131  is formed in the bottom of the inlet duct  12  around and in communication with the inlet channel  13 . 
   The head portion  1  has an outlet port  15  forming an external threading  151 . The outlet port  15  has an end face  101  from which the outlet channel  14  extends through the outlet port  15  to the inlet channel  13 . An inner-threaded hole  152  is defined in the outlet port  15  for receivingly engaging a bolt  153 . 
   An inlet return-flow prevention device  3  and a leakproof device  4  are disposed between the cylinder  2  and the head portion  1 . T inlet return-flow prevention device  3  prevents a reverse airflow in the head portion  1  so as to ensure no leakage happens on the other side when air is pumped at one side. The leakproof device  4  prevents leakage of air, especially under pressure, out of the cylinder  2  through interface between the cylinder  2  and the head portion  1 . 
   The inlet return-flow prevention device  3  is comprised of an inlet valve seat  31  and a valve piece  32 . The inlet valve seat  31  is fit into the inlet duct  12  and spaced from the bottom of the inlet duct  12 . The valve piece  32  is made of rubber material or similar materials and movably received in the inlet duct  12 . The inlet valve seat  31  defines a bore  311  extending therethrough, providing a fluid communication between inside and outside the inlet duct  12 . The valve piece  32  is movable between the bottom of the inlet duct  12  and an end face of the valve seat  31 . When the valve piece  32  reaches the end face of the valve seat  31 , the valve piece  32  blocks the bore  311  and cutting off airflow therethrough. When the valve piece  32  moves to the bottom of the inlet duct  12 , the valve piece  32  blocks the inlet channel  13  but not the radially extending grooves  131  whereby air is allowed to flow between the inlet duct  12  and the inlet channel  13  via the radially extending grooves  131 . 
   The leakproof device  4  which is formed with a rubber material has a tubular flange  43 , an annular flange  41  connected to and outward and radially extending from the tubular flange  43 , and an inclined flange  42  formed between the tubular flange  43  and the annular flange  41  and extending from a joint therebetween to hence configure the leakproof device  4  as a bowl. The tubular flange  43  is tightly fit over an outer wall of the inlet duct  12 , while the annular flange  41  abuts against a bottom face of the inlet port  10 . A terminal edge of the inclined flange  42  leans against an inside surface of the cylinder  2  when the cylinder  2  is mounted to the inlet port  10  as shown in FIG.  2 . Therefore, air leakage through the joint between the cylinder  2  and the head portion  1  is thoroughly blockaded 
   An outlet return-flow prevention device  5  is coupled to the output port  15  of the head portion  1  for preventing a reverse flow in the output port  15 , comprising an outlet valve seat  50  and a valve piece  55 . The outlet valve seat  50  comprises a substantially cylindrical body forming an inner space defined by a sidewall having an inner surface thereof with an inner threading  54  formed in the inner surface for engaging the external threading  151  of the out port  15  and thus removably attaching the outlet return-flow prevention device  5  to the outlet port  15 . A through hole  511 , substantially radial, is defined in the sidewall. The through hole  511  is made alignment with the inner-threaded hole  152  of the outlet port  15  and the bolt  153  extends through the hole  511  and engages the inner-threaded hole  152  to securely fix the outlet return-flow prevention device  5  to the outlet port  15 . 
   An annular flange  56  is formed around the cylindrical body of the outlet return-flow prevention device  5  and adjacent to a lower end thereof. An outlet bore  52  is defined in a bottom of the cylindrical body and in communication with the inner space. A plurality of radially extending grooves  53  is formed on the bottom and surrounding and in fluid communication with the bore  52 . The valve piece  55 , which is made of a rubber material, is received in the inner space of the valve seat  50  and movable between the end face  101  of the out port  15  and the bottom of the inner space of the valve seat  50 . When the valve piece  55  reaches the end face  101  of the out port  15 , the valve piece  55  blocks the outlet channel  14  and cutting off airflow therethrough. When the valve piece  55  moves to the bottom of the inner space of the valve seat  50 , the valve piece  55  blocks the outlet bore  52  but not the radially extending grooves  53  whereby air is allowed to flow between the inner space of the valve seat  50  and the outlet bore  52  via the radially extending grooves  53 . 
   A knob  6 , which is a cylindrical body having a size larger than the outlet valve seat  50 , has an inner flange  61  formed at an upper portion thereof and is fit over the valve seat  50  with the flange  61  engaging and supported by the flange  56  of the valve seat  50 . 
   A tubular portion  57  extends from the bottom of the cylindrical body of the outlet valve seat  50  with the bore  52  extending completely therethrough. The outlet valve seat  50  is received in the knob  6  so that an annular space (not labeled) is formed between the knob  6  and the tubular portion  57 . A leakproof washer  7  is received in the annular space and fit over the tubular portion  57  and positioned against the bottom of the cylindrical body of the outlet valve seat  50 . A nut  8  having inner threading  81  is fit into and fixed to the knob  6 , such as by force fitting, whereby the nut  8  is rotatable and movable in unison with the knob  6 . 
   In an inflation operation performed by the dual-direction pump of the present invention, the inner threading  81  of the nut  8  is made engaging with an external threading (not labeled) of for example an inflation valve  9  of a bicycle tire or a ball by manually rotating the knob  6 . The piston  23  of either one or both of the cylinders  2  is manually and axially driven by means of the handgrip  24 . Air inside the cylinder(s)  2  is compressed and forced through the inlet return-flow prevention device  3 , the inlet and outlet channels  13 ,  14  of the head portion  1 , and the outlet return-flow prevention device  5  into the bicycle tire or the ball. 
     FIG. 4  shows that the valve piece  32  of the inlet return-flow prevention device  3  is forced against and thus blocks the entrance of the inlet channel  13  in a pumping operation. However, as indicated by the arrows, air is still allowed to enter the inlet channel  13  through the grooves  131 .  FIG. 5  shows that when pumping operation is made in only one of the cylinders  2 , the air entering the inlet channel  13  is prevented from getting off the head portion  1  through the other cylinder  2  as the bore  311  of the inlet valve seat  31  is blocked by the valve piece  32  that is forced against the valve seat  31  by the compressed air. Thus, air can be properly and effectively pumped toward the outlet port  15  of the heat portion  1  and then entering the inflation valve  9  of the bicycle tire or the ball. 
     FIG. 6  shows that when air is pumped out through the outlet channel  14 , the valve piece  55  is moved toward and forced against, by airflow, the bottom of the outlet valve seat  50  and thus blocking the axial entrance of the outlet bore  52 . However, air is still permitted to enter the outlet bore  52  via the grooves  53 . On the other hand, a reverse airflow induced in the outlet valve seat  50  drives the valve piece  55  toward the end face  101  of the outlet ort  15  and blocking the outlet channel  14  (FIG.  7 ). This prevents the occurrence of the reverse airflow through the outlet port  15  thereby reducing resistance against pumping operation by the reverse flow. Further, the leakproof washer  7  effectively prevents leakage of compressed air through the juncture between an inflation valve  9  and the nut  8 . 
   In the above described, at least one preferred embodiment has been described in detail with reference to the drawings annexed, and it is apparent that numerous changes or modifications may be made without departing from the true spirit and scope thereof, as set forth in the claims below.