Abstract:
A band packing machine includes a body, a transmission unit, a forward-reverse unit and a tension unit. The transmission unit has a rotatable forward-reverse tension cam and a tension cam. The forward-reverse unit includes a forward-reverse motor, a forward-reverse active wheel and a forward-reverse link unit to which a forward-reverse passive wheel is connected. The tension link unit is connected to the tension passive wheel. By controlling the tension cam, the tension passive wheel and the tension active wheel clamp or loosen the bands. The tension unit and the forward-reverse unit are activated by the link units which are activated by cams so that the response time is short. The packing machine is compact and occupies less space in horizontal direction.

Description:
FIELD OF THE INVENTION 
   The present invention relates to an automatic or semi-automatic packing machine, and more particularly to a forward-reverse tension mechanism which shortens the response time of the band and the horizontal space of the machine is be reduced. 
   BACKGROUND OF THE INVENTION 
   A conventional tension mechanism for a packing machine generally includes a tension bar which is rotated with a transmission cam, a passive link, a spring, a pivot link, a clamping member, a driving member driven by a motor, a driving motor which is controlled by a controller and can be operated in forward and backward directions, an activation member on the transmission shaft for activating the controller, and a relay connected to the driving motor. When the driving motor is activated, the driving member drives the passive link to move a distance so as to push a clamping member to clamp the band which is packing an object and the tension bar is rotated so that the controller is activated by the activation member. The relay delays the activation of the driving motor so as to control the tension of the band. 
   However, in order to provide sufficient space for the rotation of the tension bar, the horizontal space of the machine has to be large enough and this limitation requires more space of the work site. When the guide mechanism pulls the band to pack the objects, the transmission shaft is rotated to control the critic position of the link of the tension bar relative to the transmission cam, a first controller sends a signal to the relay to activate the driving motor after a pre-determined delayed period to drive the driving member to rotate the link of the tension bar, so that the clamping member clamps the band. The sequence of the actions of the above mentioned parts and the time required to allow the tension bar to rotate results a long operation period which is needed to be shortened for efficient purposes. The teeth of the clamping member might damage the bands if they are too sharp, and cannot clamp the bands in position if the teeth are dull. The clamping member is pivotably connected to an end of the tension bar and the band is clamped between the clamping member and the inside of a chamber. The precision of the installation of the clamping member in horizontal direction and the surface of the chamber are required to be highly machined, or the bands cannot be pressed as desired. This required high-cost machining processes to manufacture the related parts. 
   The present invention intends to provide a forward-reverse tension mechanism which includes less number of parts, occupies less space and shortens the response time. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a band packing machine that comprises a body, a transmission unit, a forward-reverse unit, a tension unit, the transmission unit having a main shaft which is connected to a forward-reverse tension cam of the forward-reverse unit and a tension cam of the tension unit. The protrusions on the forward-reverse tension cam and the tension cam are alternatively arranged with each other. The forward-reverse unit includes a forward-reverse motor, a forward-reverse active wheel, a forward-reverse passive wheel and a forward-reverse link unit. The forward-reverse link unit includes a forward-reverse level link, a forward-reverse tension bar and a forward-reverse passive bar. The forward-reverse motor drives the forward-reverse active wheel. 
   The forward-reverse level link has an end thereof pivotably connected to the body and the other end of the forward-reverse level link is in contact with the forward-reverse cam. An end of the forward-reverse tension bar is located above the forward-reverse level link and a forward-reverse spring is connected between the forward-reverse tension bar and the forward-reverse level link. The other end of the forward-reverse tension bar is pivotally connected to an end of the forward-reverse passive bar. The other end of the forward-reverse passive bar is rotatably connected to a wall of the body. The passive bar is rotatably connected to the forward-reverse passive wheel so as to maintain the forward-reverse passive wheel to be adjacent to the forward-reverse active wheel to clamp bands. 
   The tension unit includes a tension motor, a tension active wheel, a tension passive wheel and a tension link unit. The tension link unit includes a tension level link, a tension bar and a tension passive bar. 
   The tension motor drives the tension active wheel, two respective ends of the tension active wheel and the tension passive wheel are matched by teeth. The bands pass through two respective the other ends of the tension active wheel and the tension passive wheel. The tension level link has an end rotatably connected to the body and an end of the tension level link is in contact with the tension cam. The other end of the tension level link is located corresponding to an end of the tension bar. A tension spring is connected between the tension bar and the tension level link. The other end of the tension bar is pivotably connected to an end of the tension passive bar. The other end of the tension passive bar is rotatably connected to the body. The tension passive wheel is rotatably connected to the tension passive bar so as to maintain the tension passive wheel to be adjacent to the tension active wheel. A tension spring is connected between the forward-reverse level link and the tension level link. 
   The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front view of the packing machine of the present invention; 
       FIG. 2  is a perspective view of the tension unit of the present invention; 
       FIG. 3  is an exploded view to show the forward-reverse unit of the present invention; 
       FIG. 4  is an exploded view to show the tension unit of the present invention; 
       FIG. 5  is a top plan view to show that the band is clamped by the forward-reverse unit; 
       FIG. 6  is a top plan view to show that the band is clamped by the tension unit; 
       FIG. 7  shows the tension level link, the forward-reverse level link and the cam; 
       FIG. 8  shows that the band is moved in reverse; 
       FIG. 9  shows that the status of the cam when the band is moved in reverse; 
       FIG. 10  shows that the band is in tension status, and 
       FIG. 11  shows that the status of the cam when the band is in tension status. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , the band packing machine of the present invention comprises a body  10  with a guide arch  11  on a top of the body  10  and a transmission unit  15 , a forward-reverse unit  30 , a tension unit  50 , a guide wheel unit  14 , a band reel mechanism  12 , and a pool box  13 . The band  20  is fed forward from the band reel mechanism  12  and enters the pool box  13  via the guide wheel unit  14 . A regulation member  131  of the pool box  13  sends the leading end of the band  20  into the tension unit  50  and the forward-reverse unit  30 . The band  20  is ready to enter the packing position and the guide arch  11 . The forward-reverse unit  30  and the tension unit  50  include an active wheel and a passive wheel, the active wheels and the passive wheels are controlled by link units and cooperated with springs to clamp or loosen the band  20 . The forward-reverse unit  30  and the tension unit  50  are activated by cams of transmission unit  15  so that the clamping action can be quick and the space required is reduced. 
   As shown in  FIGS. 1 to 3 , the body  10  includes an L-shaped wall  101  where the forward-reverse unit  30  and the tension unit  50  are connected. The forward-reverse unit  30  is located above the tension unit  50 . The transmission unit  15  has a main shaft  151  which is located to the other side of the wall  101 . An upper band rail  16  is connected to the body  10  and located at a top end of the forward-reverse unit  30  and a middle rail  17  is located between the forward-reverse unit  30  and the tension unit  50 . Each of the upper and middle rails  16 ,  17  is composed of two plates between which the band  20  passes. 
   The transmission unit  15  is connected to a forward-reverse tension cam  40  of the forward-reverse unit  30  and a tension cam  42  of the tension unit  50 . The protrusions on the forward-reverse tension cam  40  and the tension cam  42  are alternatively arranged with each other. 
   The forward-reverse unit  30  includes a forward-reverse motor  31 , a forward-reverse active wheel  311 , a forward-reverse passive wheel  312  and a forward-reverse link unit  32 . The forward-reverse link unit  32  includes a forward-reverse level link  33 , a forward-reverse tension bar  34  and an L-shaped forward-reverse passive bar  35 . The forward-reverse motor  31  is connected to the wall  101  and drives the forward-reverse active wheel  311  to rotate. The forward-reverse passive wheel  312  is located adjacent to the forward-reverse active wheel  311  so that the band  20  is clamped between the forward-reverse passive wheel  312  and the forward-reverse active wheel  311  as shown in  FIG. 5 . Besides, the forward-reverse level link  33  has an end thereof pivotably connected to the wall  101  of the body  10  and the other end of the forward-reverse level link  33  is connected to a forward-reverse rotary member  331  which is a bearing in this embodiment. The rotary member  331  is in contact with the forward-reverse cam  40 . An end of the forward-reverse tension bar  34  located above the middle portion of the forward-reverse level link  33  and a forward-reverse spring  36  is connected between the forward-reverse tension bar  34  and the forward-reverse level link  33 . A bolt  37  extends through the forward-reverse level link  33  to which two nuts  371  are connected, the forward-reverse spring  36  and a hole  341  in the forward-reverse tension bar  34  so that the forward-reverse tension bar  34  is biased by the forward-reverse spring  36 . The other end of the forward-reverse tension bar  34  is pivotally connected to an end of the forward-reverse passive bar  35 . The other end of the forward-reverse passive bar  35  is rotatably connected to a wall  101  of the body  10 . The middle portion of the passive bar  35  is rotatably connected to the forward-reverse passive wheel  312  so as to maintain the forward-reverse passive wheel  32  to be adjacent to the forward-reverse active wheel  311  to clamp bands  20 . In normal condition, the forward-reverse active wheel  311  and the forward-reverse passive wheel  312  clamps the band  20 . 
   As shown in  FIGS. 1 ,  2  and  4 , the tension unit  50  includes a tension motor  51 , a tension active wheel  511 , a tension passive wheel  513  and a tension link unit  52 . The forward-reverse link unit  32  includes a tension level link  53 , a tension bar  54  and an L-shaped tension passive bar  55 . 
   The main shaft  151  of the transmission unit  15  is fixed on the wall  101  and drives the tension active wheel  511 . The tension passive wheel  513  is located on a side of the tension active wheel  511  so that the band  20  can be clamped therebetween. As shown in  FIG. 6 , two respective ends of the tension active wheel  511  and the tension passive wheel  513  are matched by teeth. The bands  20  passing through two respective the other ends of the tension active wheel  511  and the tension passive wheel  513 . The tension active wheel  511  has an active groove  512  and the tension passive wheel  513  has a disk  514  which is engaged with the active groove  512  such that the bands  20  is clamped between the disk  514  and an inside of the active groove  512 . 
   The tension level link  53  has an end rotatably connected to the wall  101  of the body  10  and an end of the tension level link  53  is connected with a tension rotary member  531  which is a bearing in this embodiment, and the tension rotary member  531  is in contact with the tension cam  42 . By this arrangement, the tension level link protrudes from the forward-reverse level link. The other end of the tension level link  53  is located corresponding to an end of the tension bar  54 . A tension spring  56  is connected between the tension bar  54  and the tension level link  53 . A bolt  57  extends through the tension level link  53  to which two nuts  571  are connected, the tension spring  56  and a through hole  541  in the tension bar  54  so that the tension bar  54  is biased by the tension spring  56 . The bolt  57  that extends through the tension bar  54  is connected to a bottom nut  572  which is used to press the tension bar  54 . The other end of the tension bar  54  pivotably connected to an end of the tension passive bar  55 . The other end of the tension passive bar  55  is rotatably connected to the wall  101  of the body  10 . The tension passive wheel  513  is rotatably connected to the tension passive bar  55  so as to maintain the tension passive wheel  513  to be adjacent to the tension active wheel  511 . When the band  20  is not clamped securely, there is a gap between the tension passive wheel  513  and the tension active wheel  511  so that the band  20  is moved freely. 
   As shown in  FIGS. 2 and 3 , a limit switch  18  is connected to he wall  101  of the body  10  and located above the tension bar  34  and close to the forward-reverse spring  36 . A tension spring  44  is connected between the forward-reverse level link  33  and the tension level link  53 . 
   As shown in  FIGS. 1 and 2 , when the band  20  is fed by the guide wheel unit  14 , the pool box  13  and enters the forward-reverse unit  30 , the forward-reverse motor  31  rotates in reverse direction at high speed to feed the band  20  and sends the band  20  to a pre-set point in the guide arch  14 , The limit switch  18  detects the band  20  is in the desired position as shown in dotted lines in  FIG. 8 . 
   When packing items, the main shaft  151  is rotated counter clockwise and the forward-reverse cam  40  is co-rotated with the main shaft  151  till a pre-set stop position. As shown in  FIGS. 2 ,  8  and  9 , the forward-reverse cam  40  lifts the rotary member  331  of the forward-reverse level link  33 , and the forward-reverse bar  34  is raised as shown in solid lines in  FIG. 8 . The limit switch  18  then detects and sends a signal to a sensor to count time for retrieving the band  20 . The other end of the forward-reverse bar  34  moves upward so that the forward-reverse bar  34  is pivoted about the point on the wall  101  to drive the forward-reverse passive wheel  312  toward the forward-reverse active wheel  311  to clamp the band  20 . The forward-reverse motor  31  rotates clockwise to retrieve the band  20 . The time for retrieving the band can be set by programmable controllers. 
   After the counting for retrieving the band  20 , the main shaft  151  keeps on rotating for about 0.08 seconds, as shown in  FIGS. 10 and 11 , the forward-reverse cam  40  removes from the forward-reverse level link  33  and returns to its original position by the tension spring  44  till the operation of main shaft  151  is to let the tension cam  42  be activated to push the tension rotary member  531  downward. The other end of the tension passive bar  55  moves upward and rotates in reverse about the point on the wall  101 . This results the tension active wheel  511  and the tension passive wheel  513  move toward each other and the teeth are matched firmly, and the active groove  512  and the disk  514  clamps the band  20 . The tension motor  51  rotates clockwise to pull the band  20  and time starts to count. The main shaft  151  keeps on rotating till the tension rotary member  531  touches the lowest point of the tension cam  42 . The band  20  is to be loosened and the machine starts to proceed fusion and cutting processes to the band  20 . The main shaft  151  keeps on rotating and the tension unit  50  is disengaged from the tension cam  42  and force of the tension spring  44  returns the parts back to their original positions. The forward-reverse motor  31  is activated to send the band  20  into the pool box  13  to be ready for the next packing operation. 
   The tension spring  56  and the forward-reverse spring  36  are adjusted by moving he nuts  371 ,  571  along the bolts  37 ,  57  to control the tension bar  54  and the forward-reverse tension bar  34  so as to adjust the clamping force to the band  20  from the tension passive wheel  513 , the forward-reverse passive wheel  312 . 
   While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.