BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to a pumping device, and in particular to a pumping device that can be manually or pneumatically operated to selectively suck liquid into a container and to drain the liquid out of the container. 
   2. The Related Art 
   Replacement and/or replenishment of oil is one of the most important jobs for maintenance and repairing of automobiles. Often, the oil is drained from the oil pan by simply removing the oil drain plug that blocks a drain hole formed in the bottom of the oil pan whereby oil is allowed to freely flow out of the drain hole. This is not an efficient way for draining oil from the automobile engine and may cause undesired contamination to the surroundings. Oil pumping devices or oil draining devices are available. However, such oil pumping devices have a complicated structure and can only be manually or pneumatically operated. In Taiwan Patent Application No. 90215858, filed by the present inventor, an oil pumping device that can be operated both manually and pneumatically is disclosed. However, such as conventional device still suffers certain drawbacks that can be further improved. 
   Thus, the present invention is aimed to provide a pumping device that overcomes the drawbacks of the conventional devices. 
   SUMMARY OF THE INVENTION 
   In an aspect of the present invention, a pumping device comprises an air inlet valve and a slide switch, which, when properly set, allows air to be sucked into or expelled out of a container to increase or decrease the internal pressure of the container for oil suction and oil drainage. 
   In another aspect of the present invention, under the supply of pressurized air from an external source, the pumping device comprises first and second slide switches that, when properly set, causes increase and decrease of the internal pressure of the container due to the supply of the pressurized air and oil can be sucked into and drained out of the container accordingly. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be apparent to those skilled in the art by reading the following description of a preferred embodiment thereof, with reference to the attached drawings, in which: 
       FIG. 1  is a perspective view of a pumping device constructed in accordance with the present invention; 
       FIG. 2  is an exploded view of the pumping device of the present invention; 
       FIGS. 3A and 3B  show a relief valve mounted on a cover structure of the pumping device in normally closed position and open position, respectively; 
       FIG. 4  is a plan view of a piston of the pumping device of the present invention; 
       FIG. 5  is a cross-sectional view of the pumping device of the present invention; 
       FIG. 6  is a perspective view of a control handle of the pumping device of the present invention; 
       FIG. 7  is an exploded view of an oil hose of the pumping device of the present invention; 
       FIG. 8  is a perspective view of the pumping device showing pipes stored in a storage chamber formed inside a container body of the pumping device; 
       FIG. 9  is a cross-sectional view illustrating manual operation of oil suction with the pumping device of the present invention; 
       FIG. 10  is a cross-sectional view illustrating manual operation of oil drainage with the pumping device of the present invention; 
       FIG. 11  is a cross-sectional view illustrating pneumatically operated oil suction with the pumping device of the present invention; 
       FIG. 12  is a cross-sectional view illustrating pneumatically operated oil drainage with the pumping device of the present invention; and 
       FIG. 13  is a cross-sectional view illustrating operation of floater switches in case that an oil container is full of oil during the suction operation. 
   


   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   With reference to the drawings and in particular to  FIGS. 1 and 2 , a pumping device constructed in accordance with the present invention comprises a container body  1  having a bottom forming a base  10  that can be stepped on by a user&#39;s foot to fix the pumping device on a fixture surface during the operation of the pumping device. The container body  1  also has an open top to which a cover structure  11  is mounted. 
   Also referring to  FIGS. 3A and 3B , the cover structure  11  has a size substantially corresponding to and thus closing the top opening of the container body  1 . The cover structure  11  defines a through hole  120  that receives and retains a relief valve  12 . The relief valve  12  comprises a plug-like body (not labeled) movably received in the hole  120  and having expanded top and bottom ends. A biasing element  121 , such as a helical spring, is arranged between the expanded bottom end of the valve body  12  and a circumferential edge of the hole  120  of the cover structure  11  to normally close the hole  120  with the top expanded end of the valve  12 . When a pressure inside the container body  1  exceeds a predetermined threshold, the spring force of the biasing element  121  is overcome by the internal pressure and the valve body is moved upward to open the hole  120  thereby releasing the internal pressure. 
   A support frame  13  is arranged inside the container body  1  to maintain the container body  1  in an expanded condition without undesired deformation and/or collapse. A piston shaft  14  is formed inside the frame  13 , extending between top and bottom of the container body  1 . A piston  17  is movably received in the shaft  14 . A piston rod  16  is mounted to and extends from the piston  17  with an upper free end projecting beyond the cover structure  11  for manual operation of moving the piston  17  inside the shaft  14 . Notches  170  are defined along a circumference of the piston  17  (see  FIG. 4 ) for balance of pressure during the movement of the piston  17  inside the shaft  14  and thus easing the operation of the piston rod  16 . 
   A first transversely extending channel  15  is defined in the bottom of the container body  1 . The first channel  15  has an inner end in fluid communication with the piston shaft  14  and an outer end forming an opening in a side face of the bottom of the container body  1 . An inner check valve  150  is arranged at the inner end of the first channel  15  and between the first channel  15  and the shaft  14 . An outer check valve  151  is mounted to the outer end opening of the first channel  15 . 
   Also referring to  FIG. 5 , a second transversely extending channel  18  is defined in the cover structure  11 , having an inner end blocked by a steel ball  180  and an outer end open to the surroundings. A pressurized air nozzle  181  is mounted to the open end of the second channel  18 . The second channel  18  is connected to the outer check valve  151  of the first channel by a conduit  30  that is connected to the second channel  18  by a slide switch  3 . A first floater switch  2  is arranged inside the container body  1  and is connected to the second channel  18 . 
   Also referring to  FIGS. 5 and 6 , the cover structure  11  comprises an air inlet valve  4 , comprising a base  40  formed on the cover structure  11 . Defined in the base  40  is a T-shaped air channel including an upper transverse passage and a vertical passage in fluid communication with each other. A control handle  41 , particularly shown in  FIG. 6 , has a stem section (not labeled) movably received in the transverse passage of the T-shaped air channel. At least one groove or recess  410  is defined in the stem section, which, when the control handle  41  is manually moved, selectively blocks or opens the T-shaped air channel of the base  40 . 
   The cover structure  11  further forms a third transversely extending channel  19 , spaced from the second channel  18 . The third channel  19  has opposite open ends to which a combination of a second slide switch  5  and a vacuum generator  50 , and a pressurized air control valve  51  are mounted, respectively. A second floater switch  6  is arranged inside the container body  1  and is connected to the third channel  19 . 
   Also referring to  FIG. 7 , a wide opening  110  is formed in the cover structure  11  and communicates the interior of the container body  1 . An oil hose  7  extends through the opening  110  into the container body  1  and comprises a fastening structure  70  that fixes the oil hose  7  to the opening  110  of the cover structure  11 . The fastening structure  70  includes an anchoring base  701 , a rotatable member  702  and a clamp  703  including side wings on opposite sides of the rotatable member  702 . The rotatable member  702  and the anchoring base  701  are threadingly tightened together and are then fixed to a side flange of the opening  110  by the clamp  703  by further rotating the rotatable member  702 . 
   A storage chamber  112  in the form of an elongate tube having a closed bottom end is arranged inside the container body  1 . The storage chamber  112  forms a receptacle opening in the cover structure  11 , for receiving and retaining oil tubes and tools as shown in  FIG. 8 . 
   The device with the above described structure provides a pumping device that can be operated both manually and pneumatically for oil take-in and oil drainage, of which the operation will be described. 
   Referring to  FIG. 9 , manual operation of oil suction will be described first. To take oil in, the control handle  41  of the air inlet valve  4  is moved to a closed position and blocks the air channel of the base  40  from the surrounding atmosphere. The first slide switch  3  is open to establish communication with the atmosphere. The piston  17  is manually reciprocated in the piston shaft  14  and air inside the container body  1  is successfully expelled out of the container body  1  through the first channel  15 , the conduit  30 , and the first slide switch  3  that is now open to the surroundings. The check valves  150 ,  151  prevent reverse flow of air into the container body  1  during the expulsion of the air inside the container body  1 . A negative pressure or vacuum is thus formed inside the container body  1 , which sucks oil into the container body  1  through the oil hose  7 . 
   Referring now to  FIG. 10 , with which a manual drainage of oil will be explained, the control handle  41  of the air inlet valve  4  is moved to an open position to allow communication of the channel of the base  40  with the surrounding atmosphere. The first slide switch  3  is shut off. The communication of the interior of the container body  1  with the surrounding atmosphere is blocked by the steel ball  180  inside the second channel  18 . By manually and reciprocally moving the piston  17  with the aid of the piston rod  16  inside the shaft  14 , the surrounding air is taken into the container body  1  through the air inlet valve  4 . Consequently, internal pressure inside the container body  1  is continuously increased, which pressurizes the oil contained inside the container body  1  and eventually forces the oil to drain out of the container body  1  through the hose  7 . 
   Referring now to  FIG. 11 , oil can be sucked into the container body  1  in a pneumatic manner, rather than manually. The pressurized air control valve  51  is opened to receive pressurized air from a pressurized air source. The pressurized air passes through the second slide switch  5  and the vacuum generator  50 , forming a negative pressure or vacuum inside the third channel  19 , which vacuum moves a one-way valve member of the second floater switch  6  to such a position where a gap is formed. Air inside the container body  1  is discharged through the gap and a vacuum is induced inside the container body  1  to such oil into the container body  1  through the hose  7 . 
   Referring to  FIG. 12 , pneumatic drainage will now be explained. The first slide switch  3  is shut off. Pressurized air is supplied to the pressurized air nozzle  181  and flows through the second channel  18 . With one-way valve members of the floater switches  2 ,  6  moved upward to shut off the switches  2 ,  6 , the pressurized air are trapped in the container body  1 , which increases the internal pressure of the container body  1  and thus expelling the oil contained inside the container body  1  out of the container body  1  through the hose  7 . 
   It is noted that the floater switches  2 ,  6  function as a safety device, which, when the container body  1  is full of oil in the oil suction operation, both manual oil suction and pneumatic oil suction, are driven upward by the buoyancy thereof to block the channels for air and thus stopping suction of further oil into the container body  1 . This is illustrated in  FIG. 13 . 
   Although the present invention has been described with reference to the preferred embodiment with reference to the drawings thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.
A pumping device includes a container having a cover structure. A piston is movably received in the container and is manually operable. The cover structure has an air inlet valve and a slide switch, which, when properly set, allow air to be sucked into or expelled out of the container by the manual operation of the piston to increase or decrease the internal pressure of the container for oil suction and oil drainage. The pumping device also includes another slide switch, whereby when both slide switches are properly set, the internal pressure of the container is increased or decreased due to the supply of pressurized air from an external source and oil can be sucked into and drained out of the container accordingly.