Abstract:
An electric heat sealer for sealing workpieces such as plastic bags or the like includes a casing defining a battery chamber, a press bar pivotally connected to the casing, a sealing mechanism supported on a compression spring in a spring holder inside the casing, and a safety device. The sealing mechanism is electrically connected to produce heat for sealing the workpiece being put thereon when the press bar pressed against the sealing mechanism. The safety device breaks the electrical circuit when the apparatus is not in use.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an electric heat sealer, and more particularly to an electric heat sealer which can be controlled to break the electric circuit when the apparatus is not in use, so as to prevent an electric connection by a false action.  
         BACKGROUND OF THE INVENTION  
         [0002]    A variety of electric heat sealers have been developed for home use, and have appeared on the market. An example of such a device is disclosed in U.S. Pat. No. 5,142,123.  
           [0003]    Conventional electric heat sealers are functional for sealing plastic bags and the like. However, these electric heat sealers have no safety control means. When an electric heat sealer is touched by an external force, the sealing mechanism may be electrically connected to produce heat, potentially causing an accident to occur.  
           [0004]    A need exists for an electric heat sealer which eliminates the aforesaid problem, and which is handy and safe in use.  
         SUMMARY OF THE PREFERRED EMBODIMENTS  
         [0005]    In accordance with one aspect of the present invention, there is provided an electric heat sealer comprising a casing, a battery chamber, a spring holder, a sealing mechanism, a press bar, and a safety device. The casing holds the battery chamber, the spring holder, the sealing mechanism and the safety device on the inside. The battery chamber comprises a front upright support; a rear upright support; a first front terminal plate and a second front terminal plate respectively mounted on the front upright support; a pair of rear terminal plates respectively mounted on the rear upright support; a first metal contact plate mounted on the front upright support and connected the first front terminal plate; and a second metal contact plate mounted on the front upright support and spaced from the second terminal plate by a gap. The second terminal plate is forced into contact with the second metal contact plate when a battery set is installed in the battery chamber. The spring holder is mounted in the casing and spaced between the first metal contact plate and the second metal contact plate. The sealing mechanism is mounted in the casing and moved up and down relative to the first and second metal contact plates.  
           [0006]    The sealing mechanism comprises a heat insulative base; an electric wire; two metal locating plates; and a compression spring. The heat insulative base comprises a protrusive middle portion. The electric heating wire is mounted on the protrusive middle portion of the heat insulative base. The metal locating plates are fixedly fastened to the heat insulative base at two opposite sides and respectively connected to two opposite ends of the electric heating wire. The compression spring is connected between the spring holder and the protrusive middle position of the heat insulative base.  
           [0007]    The press bar has a fixed end pivotally connected to one end of the casing and a free and fixedly mounted with a heat insulative press block. The heat insulative press block is forced against the protrusive middle portion of the heat insulative base of the sealing mechanism when the press bar is depressed.  
           [0008]    The safety device comprises a safety switch with two opposite terminals. The safety switch has two lead wires respectively extended from the two opposite terminals thereof and respectively connected to the second terminal plate and the second metal contact plate.  
           [0009]    In a preferred embodiment, the inventive electric heat sealer further includes a protective frame pivotally connected to the casing and pivotable between a first position and a second position. In the first position, the protective frame is spaced between the heat insulative base of the sealing mechanism and the heat insulative press block of the press bar. In the second position, the protective frame is pivoted out of the space between the base and the press block.  
           [0010]    Preferably, the electric heat sealing wire and the press block are covered by heat insulative sheets, which preferably are comprised of a heat-resistant material such as a Teflon mesh.  
           [0011]    In another preferred embodiment, the inventive heat sealer further includes a cover device for the casing. The cover device has defined therein an opening through which the protrusive middle portion of the heat insulative base of the sealing mechanism extends out of the casing. More specifically, the cover device includes a front cover plate disposed on a front portion of the casing, a rear cover plate disposed on a rear portion of the casing, and an intermediate cover plate disposed on a middle portion of the casing over the battery chamber.  
           [0012]    In accordance with another aspect of the present invention, there is provided an electric heat sealer which includes a casing; a cover device; first and second metal contact plates; a sealing mechanism; resilient means, such as a spring, piston or the like, biasing the sealing mechanism in an upward direction; operating means pivotally connected to the casing; and a safety device.  
           [0013]    The cover device covers the casing and has an opening formed therethrough. The first and second metal contact plates are mounted within the casing below the opening in the cover device. The sealing mechanism is mounted in the casing and moves up and down relative to the first and second metal contact plates. The sealing mechanism includes: a heat insulative base having a protrusive middle portion; an electric heating wire mounted on the protrusive middle portion of the heat insulative base, the electric heating wire having two opposite ends; and two metal locating plates mounted on the heat insulative base and respectively connected to the opposite ends of the electric heating wire.  
           [0014]    The resilient means biases the sealing mechanism in an upward direction so that the protrusive middle portion of the heat insulative base extends through the opening in the cover device. The operating means is pivotally connected to the casing and extends above the opening in the cover device. The operating means is movable downwardly to engage an object to be sealed which is supported on the protrusive middle portion of the heat insulative base extending through the opening and urge the heat insulative base downwardly and cause the metal locating plates to engage the metal contact plates. This causes electrical current to flow through and heat the electric heating wire when the metal contact plates are connected to a source of electrical current.  
           [0015]    The safety device selectively prevents electrical current from flowing through the electric heating wire.  
           [0016]    In a preferred embodiment, the inventive heat sealer is adapted to be supplied with electrical current from at least one current source selected from the group consisting of a DC current source and an AC current source. Particularly, the inventive heat sealer is adapted to be supplied with electrical current from both a DC current source and an AC current source.  
           [0017]    More particularly, the inventive heat sealer is adapted to be supplied with electrical current from a DC current source which is a battery set. In this embodiment, the casing defines a battery chamber adapted to receive a battery set, the battery chamber including a front upright support; a rear upright support; first and second front terminal plates respectively mounted on the front upright support; a pair of rear terminal plates respectively mounted on the rear upright support; a first metal contact plate mounted on the front upright support and connected to the first front terminal plate; and a second metal contact plate mounted on the front upright support and spaced from the second terminal plate by a gap. The second terminal plate is forced into contact with the second metal contact plate when a battery set is installed in the battery chamber.  
           [0018]    Preferably, the safety device includes a safety switch having two opposite terminals and two lead wires respectively extending from the two opposite terminals thereof and respectively connected to the foregoing second terminal plate and the second metal contact plate.  
           [0019]    In accordance with a further aspect of the present invention, there is provided an electric heat sealer comprising: a casing having an opening formed therethrough; first and second metal contact plates mounted within the casing below the opening; a sealing mechanism as described above, the sealing mechanism being mounted in the casing and moving up and down relative to the first and second metal contact plates; resilient means biasing the sealing mechanism in an upward direction so that the protrusive middle portion of the heat insulative base extends through the opening in the casing; operating means pivotally connected to the casing and extending above the opening in the casing as described above; and a safety device which selectively prevents electrical current from flowing through the electric heating wire.  
           [0020]    Other objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description. It is to be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not limitation. Many changes and modifications within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    The invention may be more readily understood by referring to the accompanying drawings in which  
         [0022]    [0022]FIG. 1 is an exploded view of an electric heat sealer according to the present invention.  
         [0023]    [0023]FIG. 2 is another exploded view of the present invention.  
         [0024]    [0024]FIG. 3 is a perspective view of the present invention when viewed from the front side.  
         [0025]    [0025]FIG. 4 is another perspective rear side view of the present invention when viewed from the rear side.  
         [0026]    [0026]FIG. 5 is a sectional view of the present invention before operation.  
         [0027]    [0027]FIG. 6 is another sectional view of the present invention, showing the press bar pressed down.  
         [0028]    [0028]FIG. 7 is an enlarged view showing a flat metal contact plate and a front terminal plate separated by a gap.  
         [0029]    [0029]FIG. 8 is a circuit diagram showing the connection of an embodiment of a safety device of the invention (a safety switch) to the flat metal contact plate and front terminal plate of FIG. 7. 
     
    
       [0030]    Like numerals refer to like parts throughout the several views of the drawings.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    Referring to FIGS.  1 - 4  and  7 , a first embodiment of an electric heat sealer in accordance with the present invention includes a casing  10 , a spring holder  11 , a press bar  20 , a battery chamber  30 , a sealing mechanism  40 , and a safety device  70 .  
         [0032]    The battery chamber  30  is defined within the casing  10 . The battery chamber  30  comprises a front upright support  31 , a rear upright support  32 , a pair of front terminal plates  33  and a rear terminal unit having a pair of rear terminal plates  34  respectively mounted on the front upright support  31  and the rear upright support  32 . When battery cells (not shown) are installed in the battery chamber  30 , the positive and negative terminals of the battery cells are respectively connected to the metal contact plates  33 ,  34 .  
         [0033]    A pair of flat metal contact plates  331  are mounted on the front upright support  31 . One flat metal contact plate  331  is directly connected to one front terminal plate  33 . Alternatively, the two plates  331  and  31  can form a single unit. The other flat metal contact plate  331  is spaced from the other front terminal plate  33  by a gap  332 .  
         [0034]    The spring holder  11  is mounted in the front upright support  31  between the flat metal contact plates  331 .  
         [0035]    The sealing mechanism  40  is mounted within the casing  10 , comprising a heat insulative base  41 , an electric heating wire  42 , two metal locating plates  43 , a heat resisting cover sheet  44 , and a compression spring  45 . The heat insulative base  41  comprises a protrusive middle portion  411 . The locating plates  43  are fasted to two opposite sides of the heat insulative base  41  to hold the electric heating wire  42  on the protrusive middle portion  411 . The heat resisting cover sheet  44  is covered on the heat insulative base  41  over the electric heating wire  42  to protect the electric heating wire  42 . The heat insulative cover sheet  44  preferably is a meshed member, made from a heat-resistant material such as Teflon, providing a smooth surface. The heat insulative base  41  has a bottom mounting hole  412  at the bottom of the protrusive middle portion  411 . The bottom mounting hole  412  is preferably a circular hole. The compression spring  45  has a bottom end received in the spring holder  11 , and a top end inserted into the bottom mounting hole  412 . The diameter of the compression spring  45  fits the circular bottom mounting hole  412  of the heat insulative base  41 . Because the sealing mechanism  40  is supported on the compression spring  45 , it can be moved up and down in the casing  10  and is biased in the upward direction.  
         [0036]    The press bar  20  comprises a heat insulative press block  21  at one end facing the protrusive middle portion  411  of the heat insulative base  41  of the sealing mechanism  40 , a heat resisting cover sheet  22  covered on the heat insulative press block  21 , and a pair of lugs  23  bilaterally disposed at an opposite end. The lugs  23  have a respective pivot pin  231  at an inner side respectively inserted into two transverse pivot holes  12  at one end of the casing  10 . The heat resisting cover sheet  22  of the press bar  20  and the heat resisting cover sheet  44  of the sealing mechanism  40  are preferably made from same material, such as a Teflon mesh. Further, a spring plate  24  is provided between the press bar  20  and the casing  10  to impart an upward bias to the press bar  20 . Because of the arrangement of the spring plate  24 , the press bar  20  is normally maintained in an upward position to prevent direct contact between the heat resisting cover sheet  22  at the press bar  20  and the heat resisting cover sheet  44  at the sealing mechanism  40 .  
         [0037]    The safety device  70  is for open circuit protection. Safety device  70  preferably includes a safety switch  71  and a protective frame  73 . In the particular embodiment illustrated in FIGS. 2 and 4, the safety switch  71  is mounted in the casing  10  at the rear thereof. Safety device  70  has two lead wires  72  respectively extending from two opposed terminals thereof and respectively connected to one front terminal plate  33  (which is not directly connected to the corresponding flat metal contact plate  331 ) and one flat metal contact plate  331  (which is not directly connected to the corresponding front terminal plate  33 ). See FIG. 8.  
         [0038]    When the electric heat sealer is in use, the safety switch  71  is switched by a user to the “on” position. When the safety switch is in the “on” position, the gap  332  is bridged, enabling current to flow from terminal plate  33  to metal contact plate  331  as shown in FIG. 8. When the electric heat sealer is not in use, the safety switch  71  is switched by the user to the “off” position to keep the lead wires  72  in an open circuit state and prevent current from flowing from terminal plate  33  to contact plate  331  in FIG. 8. That is, the safety switch is a safety device that is adapted to selectively prevent electrical current from flowing through the electric heating wire. “Selectively” denotes that a user chooses a position which opens or closes the electric circuit and sets the device in the chosen position. The device remains in the selected state until the user changes the state of the device. Safety switch  71  can be a mechanical switch, an electrical device or any other device which permits selective prevention of electrical current flow.  
         [0039]    Depressing the press bar  20  against the sealing mechanism  40  does not close the electric circuit when the safety switch  71  is set at the “off” position.  
         [0040]    The protective frame  73  is pivotally connected to the casing  10  on the outside of the casing at the same end as the sealing mechanism  40 . When the electric heat sealer is not in use, the protective frame  73  is pivoted upwards and retained between the heat insulative block  21  of the press bar  20  and the protrusive middle portion  411  of the heat insulative base  41  of the sealing mechanism  40  to stop the heat insulative block  21  from contacting the sealing mechanism  40 . When in use, the protective frame  73  is pivoted outwardly and downwards to a position away from the heat insulative block  21  and the heat insulative base  41 . Thus, the protective frame, by virtue of its pivotal motion between the foregoing two positions, is also adapted to selectively prevent electrical current from flowing through the electric heating wire.  
         [0041]    Referring to FIG. 5, when the electric heat sealer is not in use, the heat insulative base  41  is biased upward by the compression spring  45  so that the locating plates  43  are spaced from the flat metal contact plates  331  to electrically disconnect the electric heating wire  42  from the battery cells. The safety switch  71  is switched to the “off” position, and the protective frame  73  is pivoted upward to the top side of the casing  10  and retained between the heat insulative press block  21  and the protrusive middle portion  411  of the heat insulative base  41  of the sealing mechanism  40 . Therefore the electric heat sealer is deactivated and performs no work.  
         [0042]    Referring to FIG. 6, when in use, the protective frame  73  is pivoted outwardly and downwards from the position above the protrusive middle portion  411  of the heat insulative base  41  preferably to the front of the casing  10 , and the safety switch  71  is switched to the “on” position to electrically connect the lead wires  72 . When the press bar  20  is pressed down, the heat insulative press block  21  is forced against the heat insulative base  41 . This causes the heat insulative base  41  to be lowered and forces the locating plates  43  into contact with the metal contact plates  331  to close the electrical circuit and heat the electric heating wire  42 .  
         [0043]    When sealing a workpiece, for example, a plastic bag, the open side of the plastic bag is placed between the protrusive middle portion  411  of the heat insulative base  41  and the heat insulative press block  21 . Then the press bar  20  is pressed down to force the locating plates  43  into contact with the metal contact plates  331  respectively. This closes the electrical circuit, thereby causing the electric heating wire  42  to be heated. The open side of the plastic bag is thus melted and sealed by the heat produced by the electric heating wire  42 . When the press bar  20  is released from the hand after use, the locating plates  43  are biased upward by the compression spring  45 , along with the rest of the heat insulative base  41 , from the metal contact plates  331  to open the electric circuit and prevent electrical current from the battery set from flowing through the electric heating wire  42 .  
         [0044]    In the foregoing embodiment, the inventive safety device includes both safety switch  71  and protective frame  73 . If desired, either of these elements can be utilized separately.  
         [0045]    Referring to FIG. 1 again, a cover device  50  is provided to cover the casing  10 . The cover device  50  is comprised of a front cover plate  51 , an intermediate cover plate  52 , and a rear cover plate  53 . The front cover plate  51  covers on the front portion of the casing  10  over the sealing mechanism  40 . The intermediate cover plate  52  covers the middle portion of the casing  10  over the battery chamber  30 . The rear cover plate  53  covers the rear portion of the casing  10 . The front cover plate  51  has defined therethrough an opening  511  through which the protrusive middle portion  411  of the heat insulative base  41  extends.  
         [0046]    Alternatively, cover device  50  can be comprised of two plates or can be formed from a single plate. That is, cover plates  51  and  52 ,  52  and  53 , or  51 - 53  can be replaced with unitary structures.  
         [0047]    Referring to FIG. 1 again, a magnetic bottom plate  80  is preferably fixedly mounted on the bottom of the casing  10 . By means of the magnetic bottom plate  80 , the electric heat sealer can be secured to a metal surface, for example a refrigerator door, by magnetic attraction.  
         [0048]    Alternative embodiments of the foregoing heat sealer are also included within the scope of the present invention. In one alternative embodiment, the rear terminal unit can be replaced with two separate rear terminal plates  34  separated by a gap, and a safety switch can be connected between the plates  34  (rather than front plated  33  and  331  as described above) while the separated front plates  33  and  331  are placed in contact or form a single element.  
         [0049]    In another alternative embodiment, electrical current can be supplied to electric heating wire  42  from an AC power source rather than a DC power source, or from both an AC power source and a DC power source. That is, the electric heat sealer can be adapted to be supplied with electrical current from at least one current source selected from an DC current source and an AC current source (including both DC and AC power sources). Exemplary alternative power sources for an electric heat sealer that can be adapted for use in the present invention are described, for example, in U.S. Pat. No. 5,142,123, which is incorporated herein in its entirety by reference. Safety switch  71  is disposed at an appropriate position in the electrical circuit between the electric heating wire and the DC and/or AC current source to selectively prevent current flow to the electric heating wire. Selection of the appropriate location for safety switch  71  in this embodiment is a matter of routine design choice for those skilled in the art.  
         [0050]    In another alternative embodiment, the cover device  50  can be disposed on the bottom of the casing  10  rather than on the top of the casing, so that, for example, a battery set can be inserted from the bottom of the electric heat sealer. In this embodiment, if desired a magnetic bottom plate can be affixed to the cover device or a plate thereof if the cover device is comprised of multiple separate plates. In this embodiment an opening through which the protrusive middle portion  411  of the heat insulative base  41  extends is formed in an upper surface of the casing itself rather than in the cover device.