Abstract:
A device to inspect a longitudinal heat seal in tubular bag material. The seal is formed by a heated sealing bar ( 14 ). Downstream of the bar ( 14 ) is a heat sensing camera ( 20 ) that sends a signal to a central processing unit ( 21 ). The unit ( 21 ) will then identify any faults in the seal.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to packaging machines that form bags of product, the bags being formed from tubular bag material that is longitudinally sealed and transversely cut and sealed to form the bags. 
       BACKGROUND OF THE INVENTION 
       [0002]    Described in U.S. Pat. No. 4,663,917 is a packaging machine. The packaging machine receives tubular bag material to the interior of which product is delivered. The tubular bag material is formed from a web (strip) that via a former is transformed into the tubular configuration. The longitudinally extending edge portions of the web are joined so as to form a longitudinal seal. Product is delivered to the interior of the tubular bag material, with the packaging machine then transversely sealing are of cutting the tubular bag material, at longitudinally spaced locations, to form bags. 
         [0003]    If the longitudinal and/or transverse seals are not properly formed, the product can degrade. Various means have been proposed for checking the integrity of the seals. 
         [0004]    As an example, seal testing devices are described in U.S. Pat. Nos. 6,568,247, 6,202,476 and 6,041,646. 
         [0005]    Previous methods of detecting improperly formed seals have a number of disadvantages including not successful detecting faulty seals, and being unduly complex and unreliable. 
       Object of the Invention 
       [0006]    It is the object of the present invention to overcome or substantially ameliorate at least one of the above disadvantages. 
       SUMMARY OF THE INVENTION 
       [0007]    There is disclosed herein a device to inspect a longitudinal heat seal in tubular bag material, the bag material being formed of plastics material having longitudinally extending and overlapping edge portions secured together by the heat seal, the device including: 
         [0008]    a drive assembly to engage the tubular bag material to move the tubular bag material along a predetermined path in a predetermined direction; 
         [0009]    a heat sealing mechanism to engage the longitudinally extending edge portions to heat the edge portions to form said longitudinally extending heat seal; and 
         [0010]    a camera directed at the heat seal and to provide a signal indicative of the temperature of the heat seal exposed to the camera. 
         [0011]    Preferably, said camera provides a signal indicative of infrared radiation emanating from the seal to thereby provide a signal indicative of the temperature of the seal exposed to the camera. 
         [0012]    Preferably, the camera provides a signal indicative of any temperature gradient transversely across the seal. 
         [0013]    There is further disclosed herein, in combination, the above device, and a heat sealing bar to engage the tubular bag material to form the seal, the bar being supported for movement between an engaging position to engage the bag material to form the seal, and a retracted position, spaced from the engaged position so as not to be engaged with the tubular bag material, and a drive assembly operatively associated with the bar to move the bar between the engaged and retracted positions, the drive assembly also generating a signal delivered to a central process unit to provide an indication of when the bar is engaged with the tubular bag material, with the camera also delivering the camera signal to the unit. 
         [0014]    Preferably, the drive assembly includes a spring urging the bar to the engaged position, and a cylinder to move the bar from the engaged position to the retracted position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The preferred form of the present invention will now be described by way of example with reference to the accompanying drawing that schematically depicts in sectioned side elevation a device to inspect a longitudinally extending heat seal in tubular bag material to detect faults in the seal. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]    In the accompanying drawing there is schematically depicted a former  10  to which a web of packaging film is delivered. The web is in the form of a strip that engages the former surface  11  so as to be configured into a tubular configuration. Formers are and described in U.S. Pat. Nos. 7,124,559 and 7,415,809. The tubular bag material is driven in the direction  12  engaged with vacuum drive belts  13 . The suitable vacuum belt assemblies are described in U.S. Pat. Nos. 4,910,943 and 7,472,528. 
         [0017]    The packaging film has longitudinally extending edge portions that overlap when the bag material is in the tubular configuration. The overlapping longitudinally extending edge portions are engaged by a heated sealing bar  14 . The heating bar  14  is electrically heated and heats the tubular bag material to cause the plastics material thereof to melt, bond and form a longitudinal seal. 
         [0018]    Above the former  11  is a product delivery chute  15  to which batches of product are delivered so as to be located within the tubular bag material. A packaging machine downstream of the belts  13  strips the bag material, forms transverse seals and cuts individual bags of product from the tubular bag material. A suitable packaging machine is described in U.S. Pat. No. 4,663,917. 
         [0019]    The bar  14  is mounted on a supporting frame for linear movement in the direction  16 , that is a direction transverse of the direction  12 , and a direction transverse relative to the tubular bag material and longitudinal seal. The bar  14  is movable between a position of engagement with the tubular bag material to form the seal, and a retracted position spaced from the tubular bag material. 
         [0020]    A bar drive assembly  22  moves the bar  14  in the direction  16  and includes pneumatic or hydraulic cylinder  17  is attached to the bar  14 , and a valve  18 . Preferably, the cylinder  17  is pneumatically operated and receives air under pressure from the valve  18 . 
         [0021]    The bar  14  is urged to the engaged position by means of a spring  23 . Actuation of the cylinder  17  by the valve  18  moves the bar  14  in the direction  16  to move the bar  14  to the retracted position. 
         [0022]    Downstream of the bar  14  in the direction  12  is a heat sensing camera  20 . The camera  20  is provided to generate a signal indicative of the temperature of the longitudinal seal in the tubular bag material. If there is a fault in the seal, then the area of the fault will be at a lower temperature. As a particular example, the camera  20  could detect infrared radiation coming from the seal in order to provide a signal indicative of the temperature of the seal. Preferably the camera  20  is also adapted to provide a signal indicative of the temperature gradient across the seal. If the temperature gradient across the seal is not consistent, then again this is indicative of a flaw in the seal. 
         [0023]    The camera  20  sends a signal to a central processing unit  21 . The processing unit  21  is operatively associated with the packaging machine below, as well as other apparatus such as the drive mechanism for the belts  13 , to cease operations should a faulty seal be detected. In particular, the unit  21  could cease operation of the packaging machine and associated apparatus if the temperature of a portion of the seal is outside of the desired range, or the temperature gradient across the seal is not consistent. The unit  21  also controls the valve  18  and therefore is aware of the position of the bar  14  and therefore will not expect a desired temperature of the seal to be detected when the bar  14  is in the retracted position.