Abstract:
A depression container includes a vessel including a compartment and a cover for enclosing and thus sealing the compartment. An air pump draws air out of the compartment and a pressure-activated switch controls on/off of the air pump. The pressure-activated switch detects an internal pressure in the compartment. The air pump is turned on when the internal pressure is higher than a predetermined first pressure value. The air pump is turned off when the internal pressure is lower than a predetermined second pressure value. In an alternative embodiments, the pressure-activated switch detects a pressure difference resulting from a closing motion of the cover on the vessel and turns the air pump on to thereby draw air out of the compartment of the vessel. The air pump is turned off when an internal pressure in the compartment detected by the pressure-activated switch is lower than a predetermined pressure value.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a depression container that is capable of maintaining the internal pressure under a predetermined value, and more particularly to a depression container equipped with an air pump that can be activated when the internal pressure in the depression container is below a predetermined value. 
     2. Description of the Related Art 
     A typical depression container includes a one-way valve and a user may manually operate a hand air pump to draw air out of the container via the one-way valve. The internal pressure of the container is thus reduced to a relatively low valve (almost vacuum). This reduces the risk of the articles in the container from being wetted or contaminated by dust or bacteria, thereby lengthening the preserve time. It is, however, troublesome and labor-intensive for the user to reciprocatingly operate the hand air pump for many times. In addition, the user cannot know the exact internal pressure in the depression container. Furthermore, the depression container cannot provide an absolute sealing effect such that the internal pressure in the depression container may rise after a period of time and thus adversely affect preservation of the articles in the depression container. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a depression container that may automatically draw air out of the depression container after a cover is attached to enclose an open end of the depression container. The internal pressure of the depression container is reduced to a predetermined value. 
     It is another object of the present invention to provide a depression container that clearly shows the value of the internal pressure. The depression container also allows the user to reset the internal pressure desired for preserving articles. 
     It is a further object of the present invention to provide a depression container that may maintain the internal pressure thereof under a predetermined valve for a long time. 
     In accordance with a first aspect of the invention, a depression container comprises: 
     a vessel including a compartment with an open end; 
     a cover for enclosing the open end of the vessel and thus sealing the compartment; 
     an air pump for drawing air out of the compartment of the vessel; and 
     a pressure-activated switch for controlling on/off of the air pump; 
     the pressure-activated switch being capable of detecting an internal pressure in the compartment of the vessel, the air pump being turned on when the internal pressure is higher than a predetermined first pressure value, the air pump being turned off when the internal pressure is lower than a predetermined second pressure value that is smaller than the predetermined first pressure value. 
     In accordance with a second aspect of the invention, a depression container comprises: 
     a vessel including a compartment with an open end; 
     a cover for enclosing the open end of the vessel and thus sealing the compartment; 
     an air pump for drawing air out of the compartment of the vessel; and 
     a pressure-activated switch for controlling on/off of the air pump; 
     the pressure-activated switch detecting a pressure difference resulting from a closing motion of the cover on the vessel and turning the air pump on to thereby draw air out of the compartment of the vessel, the air pump being turned off when an internal pressure in the compartment detected by the pressure-activated switch is lower than a predetermined pressure value. 
     Thus, the air pump is activated by a pressure difference resulting from the closing motion of the cover, and the pump is deactivated after the internal pressure in the vessel is reduced to a first predetermined pressure value. When the internal pressure rises and exceeds a second predetermined pressure value higher than the first predetermined value, the pump is activated again until the internal pressure is reduced to the first predetermined pressure value. Thus, the articles in the vessel can be preserved for a long time by means of maintaining the internal pressure in the vessel under a predetermined low pressure suitable for preservation of articles. 
     Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a depression container in accordance with the present invention. 
     FIG. 2 is an exploded perspective view of the depression container in accordance with the present invention. 
     FIG. 3 is a sectional view of an upper portion of the depression container in accordance with the present invention. 
     FIG. 4 is a sectional view similar to FIG. 3, illustrating operation of the depression container upon closing of a cover. 
     FIG. 5 is a sectional view similar to FIG. 4, wherein the cover is moved to its fully closed position. 
     FIG. 6 is a perspective view illustrating a modified embodiment of the depression pump in accordance with the present invention. 
     FIG. 7 is an exploded perspective view illustrating a further modified embodiment of the depression pump in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 through 3, a depression container in accordance with the present invention generally includes a vessel  1 , a cover  20 , an air pump  2 , a pressure-activated switch  3 , and a battery unit  4 . 
     The vessel  1  is cylindrical and includes a closed lower end and an open upper end and thus defines a compartment  11  for receiving articles to be preserved. The compartment  11  is enclosed and thus sealed by the cover  20  that is attached to the open upper end of the vessel  1 . The cover  20  includes a sealing plate  28  (FIG.  3 ), which also serves as a mounting plate. Namely, the sealing plate  28  seals the compartment  11  and provides a base on which the air pump  2 , the pressure-activated switch  3 , and the battery unit  4  are mounted. In this embodiment, a space  21  is defined above the sealing plate  28 , and two parallel first walls  22 , two parallel second walls  23 , and a battery seat  24  are formed on top of the sealing plate  28 , best shown in FIG.  2 . Each first wall  22  includes, e.g., two slots  221  and each second wall  23  includes, e.g., two slots  231 . The sealing plate  28  farther includes a first through-hole  25  and a second through-hole  26  that are communicated with the compartment  11  of the vessel  1 , which will be described in detail later. 
     The air pump  2  includes a casing  30  and an air duct  31  extending from a bottom side of the casing  30 . The casing  30  further includes two lateral sides each having two engaging members  32  for engaging with the slots  221  of the associated wall  22 , thereby securely mounting the air pump  2  into the space  21  of the cover  20 . An airtight sleeve  33  is extended through the first through-hole  25 . The air duct  31  is mounted in the airtight sleeve  33  and thus located below the sealing plate  28 , best shown in FIG.  3 . Of course, an additional sealing plate  29  can be provided between the upper end face of the vessel  1  and the sealing plate  28  to assist in the sealing effect. 
     The pressure-activated switch  3  includes a casing  40 , a differential type pressure transducer  44  in the casing  40 , and a control chip  46 . The pressure transducer  44  includes a sensor  48  that extends downward beyond the casing  40 . The casing  40  includes two lateral sides each having two engaging members  41  for engaging with the slots  231  of the associated wall  23 , thereby mounting the pressure-activated switch  3  into the space  21  of the cover  20 . An airtight sleeve  42  is extended through the second through-hole  26 , and the sensor  48  is mounted in the airtight sleeve  42  and thus located below the sealing plate  28 , best shown in FIG,  3 . 
     The battery unit  4  is mounted to the battery seat  24  in the cover  20  for powering the pressure-activated switch  3  and the air pump  2 . 
     The pressure transducer  44  outputs a voltage in response to a difference between a reference pressure (e.g., the atmosphere) and a detected internal pressure in the compartment  11  of the vessel. Namely, the output voltage of the pressure transducer  44  is in linear proportion to the pressure difference, In this embodiment, the output voltage is 3.3V if the detected internal pressure is equal to or above a first threshold pressure value (e.g., 1.15 atm); the output voltage is 1.2V if the detected internal pressure is equal to or below a second threshold pressure value (e.g., 0.1 atm); and the output voltage is 1.5V if the detected internal pressure is equal to or above a third threshold pressure value (e.g., 0.25 atm). 
     The control chip  46  has a set of controlling programs recorded therein and includes two logic control modes M 1  and M 2  switchable by a switch  45 . When switched to the control mode M 1 , the air pump  2  is activated when the output voltage of the pressure transducer  44  is higher than or equal to 3.3V and the air pump  2  is turned off when the output voltage of the pressure transducer  44  is lower than or equal to 1.2V. When switched to the control mode M 2 , the air pump  2  is activated when the output voltage of the pressure transducer  44  is higher than or equal to 1.5V and the air pump  2  is turned off when the output voltage of the pressure transducer  44  is lower than or equal to 1.2V. 
     In use, referring to FIG. 4, the switch  45  is first switched to the control mode Ml, and the cover  20  is attached to and thus encloses the vessel  1 . During closing of the cover  20  (i.e., the cover  20  is moved downward relative to the vessel  1 ), the air inside compartment  11  of the vessel  1  is compressed and thus generates an instant pressure greater than 1.15 atm. The pressure transducer  44  of the pressure-activated switch  3  detects such a pressure and outputs a voltage higher than 3.3V The air pump  2  is thus activated under the control of the control chip  46 , thereby drawing air out of the vessel  1  (e.g. vacuumizing the vessel  1 ). The pressure in the vessel  1  is accordingly reduced. When the air pressure in the vessel  1  is equal to or below 0.1 atm, the output voltage of the pressure transducer  44  is lower than 1.2V. The air pump  2  is thus turned off. 
     The switch  45  is switched to the control mode M 2  after depression. If the air pressure in the vessel  1  rises as a result of entrance of ambient air into the vessel  1 , the sensor  48  detects the air pressure and the air pump  2  is turned on when the air pressure in the vessel  1  is equal to or above 0.25 atm upon outputting an output voltage higher than 1.5V. When the air pressure inside the vessel  1  is equal to or lower than 0.1 atm, the pressure transducer  44  outputs a voltage lower than 1.2V to turn off the air pump  2 . Thus, the air pressure in the vessel  1  is kept at about 0.1 atm. 
     It is appreciated that the switch  45  and the control modes M 1  and M 2  can be simplified. For example, the control mode M 1  is OFF, and the control mode M 2  is ON, More specifically, the pressure transducer  44  is turned on when in the control mode M 2  and is turned off when in the control mode M 1 . Thus, when in use, the user may attach the cover  20  to the vessel  1  and switch to the control mode M 2  after the cover  20  is in position. The air pump  2  is turned on when the air pressure in the vessel  1  is equal to or above 0.25 atm and the air pump  2  is turned off when the air pressure in the vessel 1 is equal to or lower than 0.1 atm. 
     In addition, referring to FIG. 6, the cover  20  may include a display  50  (e.g., a liquid crystal display) to display the air pressure in the vessel  1 . The cover  20  may further include an input device  52  for inputting the pressure value at which the articles in the vessel are to be kept. Namely, the user may change the second threshold value (0.1 atm in the above embodiment) to any desired value. The input device  52  may also be used to input the name of the articles to be preserved in the vessel  1 . 
     FIG. 7 illustrates a modified embodiment of the depression container in accordance with the present invention. The depression container includes a vessel  5 , a cover  60 , an air pump  6 , a pressure-activated switch  7 , and a battery unit  8 . 
     The vessel  5  is cylindrical and includes a closed lower end and an open upper end and thus defines a compartment  51  for receiving articles to be preserved. The compartment  51  is enclosed and thus sealed by the cover  60  that is attached to be open upper end of the vessel  5 . The cover  60  includes a sealing plate  68 , which also serves as a mounting plate, Namely, the sealing plate  68  seals the compartment  51  and provides a base on which the air pump  6 , the pressure-activated switch  7 , and the battery unit  8  are mounted. In this embodiment, a space  61  is defined above the sealing plate  68  and an annular battery seat  62 , a first cylindrical wall  63 , and a second cylindrical wall  64  are formed on top of the sealing plate  68 . The annular battery seat  62  defines a seat for receiving the battery unit  8 . The sealing plate  68  further includes a first through-hole  65  surrounded by the first cylindrical wall  63  and a second through-hole  66  surrounded by the second cylindrical wall  64 , The through-holes  65  and  66  are communicated with the compartment  51  of the vessel  5 . 
     The air pump  6  includes a casing  70  and an air duct  71  extending from a bottom side of the casing  70 . An outer threading  72  is defined in an outer periphery of the casing  70  for engaging with an inner threading  631  of the first cylindrical wall  63 , thereby securely mounting the air pump  6  to the fist cylindrical wall  63 . An airtight sleeve  74  is extended through the first through-hole  65 . The air duct  71  is mounted in the airtight sleeve  74  and thus located below the sealing plate  68 . Of course, an additional sealing plate  69  can be provided between the upper end face of the vessel  5  and the sealing plate  68  to assist in the sealing effect. 
     The pressure-activated switch  7  includes a casing  80 , a differential type pressure transducer  84  in the casing  80 , and a control chip  86 . The pressure transducer  84  includes a sensor  88  that extends downward beyond the casing  80 . The casing  80  includes an outer threading  81  in an outer periphery thereof for engaging with an inner threading  641  of the second cylindrical wall  64 , thereby mounting the pressure-activated switch  7  into the space  61  of the cover  60 . An airtight sleeve  87  is extended through the second through-hole  66 , and the sensor  88  is mounted in the airtight sleeve  87  and thus located below the sealing plate  68 . 
     The battery unit  8  is mounted to the battery seat  62  in the cover  60  for powering the pressure-activated switch  7  and the air pump  6 . 
     The sealing plate  68  further includes preserved passages  611  allowing electrical connection between the battery seat  62  and terminals  82  and  73  respectively on the pressure-activated switch  7  and the air pump  6 . Operation of the modified embodiment is identical to that of the first embodiment illustrated in FIGS. 1 through 5. 
     Although the invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the invention as hereinafter claimed.