Abstract:
An apparatus to test integrity of a seal of a package. The apparatus includes a height detector detecting a height of the package, a test portion determining the integrity of the seal based upon a position of the test portion as a function of time when contacting the package, and a mover moving the test portion into an initial position of contact with the package based upon the detected height. The test portion includes a test head contacting the package, and the mover includes a servo motor driving the test head, and a ball screw linking the servo motor and the test head.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority to UK Application No. 0116266.8, filed Jul. 3, 2001 and UK Application No. 0126677.4, filed Nov. 6, 2001, the disclosures of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a package handling apparatus, particularly to an apparatus to test the seal quality of gas-filled packages and to prepare the packages for such testing. 
   2. Description of the Related Art 
   Many types of apparatus to test the integrity of gas-filled packages, such as flexible pillow type bags filled with chips or other snack foods, have been proposed. Generally, a test head is lowered onto a package to apply a load which will cause a leaky package to deflate. To achieve a measurable effect in a short time, large loads must be applied (e.g. 2.5 kg), with considerable risk of damage to the contents of the package. This system has a high inertia and is therefore slow, inaccurate and inconsistent. Furthermore, this system is difficult to adjust, e.g., for adapting to different package types. Thus, after each test, the head is raised to a maximum height, wasting much time. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the present invention to provide an apparatus which is faster, more efficient, and more adaptable than general designs. 
   Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
   The foregoing and other objects of the invention are achieved by providing an apparatus to test integrity of a seal of a package. The apparatus includes a height detector detecting a height of the package, a test portion determining the integrity of the seal based upon a position of the test portion as a function of time when contacting the package, and a mover moving the test portion into an initial position of contact with the package based upon the detected height. The test portion includes a test head contacting the package, and the mover includes a servo motor driving the test head, and a ball screw linking the servo motor and the test head. 
   The foregoing and other objects of the invention are also achieved by providing an apparatus to test integrity of a seal of a package, including height detecting means for detecting a height of the package; determining means for determining the integrity of the seal based upon a position of the determining means when contacting the package; and moving means for moving the determining means into an initial position of contact with the package based upon the detected height. 
   The foregoing and other objects of the invention are also achieved by providing an apparatus to test integrity of a seal of a flexible gas-filled package having a pillow shape, including a conveyor conveying the package through the apparatus; a height detector detecting a height of the package; a test portion determining the integrity of the seal based upon a position of the test portion as a function of time when contacting the package; and a mover moving the test portion into an initial position of contact with the package at a height above the conveyor which is based upon the detected height of the package. 
   The foregoing and other objects of the invention are also achieved by providing a method to test integrity of a seal of a package, including detecting a height of the package; contacting the package with a testing device, including moving the testing device to contact the package at an initial position of contact determined by the detected height; and determining the integrity of the seal based upon a position of the testing device as a function of time when contacting the package. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and advantages of the invention will become apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which: 
       FIG. 1  is a schematic side elevational view of an apparatus according to an embodiment of the present invention; 
       FIGS. 2A and 2B  are plan and side elevation views, respectively, of a roller array of the conditioning section of  FIG. 1 ; 
       FIG. 3  is a front elevational view of a light curtain device to gauge package height of  FIG. 1 ; 
       FIGS. 4A and 4B  are plan and side elevational views, respectively, of the testing station of  FIG. 1 ; 
       FIGS. 5A and 5B  are enlarged plan and side elevational views, respectively, of the actuator assembly of the testing station of  FIGS. 4A and 4B ; 
       FIG. 6  is a schematic graph showing test results; and 
       FIG. 7  is a side elevational view showing the testing station of  FIG. 1  downstream of a package sensing apparatus, according to an additional embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
     FIG. 1  shows part of a production line to receive packages  40  (see  FIG. 3 ) from a package filling and sealing apparatus, and to test the packages  40  prior to placement in trays or cartons. As an example, the packages  40  may be flexible pillow type bags filled with articles such as chips or other snack foods. Generally, between the package filling and sealing apparatus (which may be off-line) and the illustrated apparatus, there are one or more intermediate stations, e.g., to orient the packages  40 . 
   The packages  40  are carried on a conveyor belt  10  or other conveying unit having a direction of displacement as shown by the arrow  12 . In the embodiment shown in  FIG. 1 , this conveying direction slopes gently upwards. 
   The packages  40  are conveyed to a conditioning station  14 . Here, the articles are agitated by passage over a rumbling conveyor  16  while being pressed gently from above by an overhead conveyor  18 , with a lower run being pressed down by a pressing element  20 , having, for example, a catenary shape. 
   The arrangement of the overhead conveyor  18  and pressing element  20  may be generally as described in application WO 95/32123 to Bennett. This application discloses the use of a rumbling conveyor, in the form of a conveyor belt having two square-section rollers in contact with the underside of the conveyor belt. Upon rotation, the corners of the square section rollers cause the conveyor belt to repeatedly rise and fall in a flapping motion. Although not illustrated herein, this is one arrangement that may be used. 
   The arrangement of the overhead conveyor  18  and the pressing element  20  may also be as shown in  FIGS. 1 ,  2 A and  2 B.  FIGS. 2A and 2B  show a series of tapered rollers  22  having horizontal axes of rotation, alternate rollers  22  tapering on opposite ends but being rotated in the same direction to move the package along while being jolted. This provides a thorough but gentle shaking. Furthermore, the gaps between the rollers  22  allow debris (e.g., chips from broken packages) to fall through, preventing the debris from passing to the next station. 
   Downstream of the conditioning station  14  is a testing station  30 . The packages  40  are conveyed through the testing station  30  on the conveyor belt  10 . Before entering the testing station  30 , the packages  40  pass through a curtain of light, extending between an emitting array  32 , and a photocell array  34 , arranged at respective sides of the conveyor belt  10 , as shown in FIG.  3 . Light, for example, laser light, is conveyed to a vertical line of emission points in the emitting array  32  along a series of fiber optic cables  36 , and the individual photocells thereto. Other light transmitting devices may also be used in place of the fiber optical cable  36 . As shown in  FIG. 3 , a package  40  partially occludes the light curtain. The outputs of the photocells are fed along a cable  12  to a remote control unit (RCU) employing a computer  43 , or other data processing device (FIG.  1 ), which uses the output data to identify a maximum height of the package  40 . As illustrated herein, the package  40  is generally pillow-shaped after conditioning, with the upper surface of the package  40  being supported primarily by the cushion of gas (air) within the package  40 , rather than by contact with the solid articles. Although pillow-shaped packages are described herein, the present apparatus may be used to test gas-filled packages of any shape. 
   Since the speed of the conveyor belt  10  is known, the passage of the package  40  through the light curtain can also be used to measure the length of the package  40 . These measurements can be used to identify the type of package  40  from a range of the packages  40  that differ in dimensions, and whose data have been fed into the computer  43 . 
   The testing station  30  includes a test head  50  (FIG.  4 B), and unit to controllably move the test head  50  towards and away from the conveyor belt  10 . The test head  50  is shown as having an array of non back-pressure rollers  53  which extend transversely across the conveyor belt  10  and define a main contact surface portion  54 . This contact surface portion  54  is parallel with the surface of the conveyor belt  10 , bending upwardly at the upstream side to define an angled lead-in surface  56 . It is also possible to use a belt driven in synch with the conveyor belt  10 . 
   The test head  50  further includes a body  52 , which is mounted to two pairs of levers  58 ,  60  at each lateral side of the body  52 . The lower ends of the lower limbs of corresponding levers  58 ,  60  are linked by shafts  62 . Although the levers  58 ,  60  generally have an L-shape in  FIG. 4A , other shapes are also possible. 
   The testing station  30  further includes a fixed body  70 . The levers  58 ,  60  are mounted to the fixed body  70  by pivot shafts  72 , which connect corresponding levers  58 ,  60  at the intersection of their limbs. Thus, the test head  50  is carried by parallelogram linkages, so that it moves with its main contact surface portion  54  maintained parallel with the surface of the conveyor  10 . At each side of the testing station  30 , the upper limbs of the two levers  58 ,  60  are linked to a respective longitudinally extending shaft  74  (FIG.  4 A). The shafts  74  are linked by a transverse rod  76  which passes through a displaceable piston sleeve  78 . The piston sleeve  78  is constrained by the parallelogram linkages to move approximately horizontally (actually, through an arc), and the movement thereof causes pivoting of the levers  58 ,  60 , with concomitant rising or falling of the test head  50 . 
   The piston sleeve  78  is linked to a motor, for example, a servo motor  80 , via, for example, a ball screw coupling. This employs a high-resolution load-matched ball screw for maximum sensitivity and reduced backlash. Furthermore, the test head  50  is biased for zero backlash measurements. 
   The servo motor  80  can be operated in torque control mode, so that an accurately known force is applied downward to the test head  50 . This is made possible by the simple and direct mechanical coupling between the servo motor  80  and the test head  50  (via the ball screw and the lever arms). The motor  80  is pivotally mounted to the fixed body  70  through stub shafts and pivots slightly to allow the arcuate movement of the piston sleeve  78 . 
     FIGS. 5A and 5B  are enlarged views of the servo motor  80 , the piston sleeve  78 , and the actuation therebetween. 
   In normal use, the arrival of the package  40  to be tested is detected by the light curtain device, providing data indicating the height of the package  40 . This information is used to control the servo motor  80 , so that the test head  50  is raised sufficiently to allow the package  40  to pass beneath. The test head  50  does not need to be raised to the maximum height each time. A further possibility is for the heights of a multiplicity of packages  40  to be recorded, and for the computer  43  to determine an expected package height range or “tolerance band”. This can be used to provide a standard height to which the test head  50  is raised, and/or to cause rejection of packages  40  which are outside the tolerance band. This could, for example, prevent the test head  50  from being lowered onto debris such as escaped chips which had reached the testing station  30 . 
   When the light curtain has determined that a proper package  40  has passed, the computer  43  can determine precisely when the package  40  will be beneath the test head  50 , since the computer  43  also receives data about the speed of the conveyor belt  10 . The test head  50  is therefore lowered by actuation of the servo motor  80 , in a controlled fashion, with controlled torque. The height of the test head  50  is monitored, generally by monitoring the operation of the servo motor  80 .  FIG. 6  is a schematic graph showing the height (h) of the test head  50 , versus distance (s) traveled by the package  40 . Initially, when the test head  50  contacts a balloon-like article, there is a tendency to sink down and rise up again, giving a dip region  81 . Furthermore, oscillations are damped by the servo motor  80 . For a non-leaking package  40 , the dip is followed by a horizontal region  82 , as the test head  50  applies a constant torque and is supported at a constant height. However, if the package  40  leaks, the test head  50  will descend, leading to the downward gradient of broken line  84 . A leaky package  40  can be detected by noting and comparing the values of the height parameter at two spaced intervals A and B. The test assembly can also be used in a positional speed mode. 
   To determine the appropriate test torque, a destruction test may be carried out on a package  40  as follows. After conditioning, the package  40  is placed beneath the test head  50 , with the conveyor belt  10  stationary. The servo motor  80  is then operated to cause the test head  50  to descend, until the package  40  bursts. The pressure (or torque) at which the bursting happens is noted, and a fraction of this pressure (e.g., 40%) is then used as the standard applied value for testing similar packages  40 . 
   The test head  50  measures both torque and height, which can be done using the servo motor  80 . It is also possible to include a load cell to measure torque/pressure values. 
   The seal test apparatus of the present invention can handle packages  40  very gently, reducing the risk of bursting or scratching. Typically, the load applied is 1.5 kg or less, but greater loads may also be applied. The extremely sensitive height sensing (due to the direct linkage to the servo motor  80  via the ball screw) enables even tiny leaks to be detected, at high travel speeds. An output of  150  packages 40 per minute or more can be achieved. 
   A conventional apparatus must be mechanically reset each time the product changes or if any parameter is varied. With the present apparatus, changes in height are automatically accounted for by the emitting array  32  and the photocell array  34 . If necessary, recalibration of the head  50  is simple, as described above. Specifically, no mechanical alteration is required since the computer  43  controls the torque to be applied by the servo motor  80 . The ability to vary the test load to match the type or product provides the ‘best-fit’ compromise between maximum accuracy of leakage measurement and product fragility. Depending on the application, the user can select between using the maximum possible pressure to detect the smallest leaks or the minimum pressure to minimize product damage or burst packages  40 . 
   The test head  50  is kept in contact with the package  40  only during the test period, thereby minimizing the risk of product jams. The default direction of movement for the test head  50  is upwards, away from the package  40 , leaving pathways clear except during power up/down phases. 
   Stability of test head geometry is crucial due to the fine measurement tolerances required, especially with short contact periods at high speed. Sanitation procedures may require the test head  50  to be removed and replaced occasionally. This can be done precisely without the need for re-calibration. Problems with product debris affecting or causing variations in the home point are eliminated. There is no need to clear product from the machine during start-up as with previous designs. Parameters can be altered ‘on-the-fly’ and will take immediate effect without the need to stop the machine. 
   The treatment of ‘gross leakers’, below minimum height packages  40  and above maximum height packages  40  can be handled individually to suit customer requirements and plant layout. Air divert direction, delay and duration can be individually selected on the remote console of the RCU. 
   The conveyor belt  10  is accurately controlled to maximize measurement stability and repeatability. Speed can be reduced for longer test periods as typically required for larger packages  40 . Speed can be profiled to maximize test times at higher speeds for greater accuracy. 
   The feedback from the test-head  50  needs to match as closely as possible the height and hence the deflation curve of the product as it passes underneath. Servo feedback or non-contact height measurement may be used to provide an accurate (approximately 1 μm), linear reading. 
     FIG. 7  shows a test section  30 ′ according to a second embodiment of the present invention, having an associated sensing apparatus  90 . The test section  30 ′ may be essentially the same as the test section  30  already described, with a test head  50 ′ mounted on L-shaped levers  58 ′,  60 ′ movable by a servomotor  80 ′. The sensing apparatus  90  may take the place of the light curtain device  32 ,  34 , and includes a device to contact the packages  40 , such as a pivotable endless belt  92  (shown in several angular positions) extending in the package conveying direction (see arrow A). Other contact devices are also possible. The belt  92  is pivotally mounted by a transverse pivot  94  at an upstream or drive side (relative to the package conveying direction A). The belt  92  is driven by a motor  96  or other drive unit, via a linking mechanism such as a drive belt  98 . A measuring device, for example, an encoder  100  (in this example a 2000 per rev encoder) measures the angle of the belt  92 . 
   The belt  92  is lightly biased in a counter-clockwise direction so that the free downstream end is close to or in contact with the upper surface of the conveyor belt  10 . The package  40  moved by the conveyor  10  enters the nip defined between the conveyor  10  and the pivotable belt  92 , and contacts the belt  92 , whose surface is moving at substantally the same speed as the conveyor. The contact causes the belt  92  to pivot clockwise sufficiently to allow the package to pass beneath. In the process, the package  40  may undergo some stabilization of its contents. The amount of pivoting is measured by the encoder  100 . This provides data to control the servo motor  80  of the test section  30 ′ to position the test head  50 ′ appropriately. 
   This device enables package  40  to be fed into the test section  30 ′ smoothly. The test head  50 ′ is positioned to the correct height for each package  40  by feedback from the encoder  100 . This allows a much more controlled application of the test head  50 ′ force onto the package  40 . Feedback is consistent because the package  40  will be stabilized to some extent by the pivotable belt  92 . The belt assembly has been designed to be as light as possible to prevent seal damage or popping of packages  40  caused by the inertia of the present heads. 
   The light curtain device is described as including fiber optic cables, laser light, and photocells. However, the present invention is not limited to any particular type of radiation, emitter or detector. The sensing apparatus  90  is described as including endless belt  92 , motor  96 , drive belt  98 , and encoder  100 . However, the present invention is not limited to any particular type of contact surface, drive source, force transfer device, or measurement device. The testing station  30  is described as including levers  58 ,  60  and rollers  53 , however, the present invention is not limited to any particular type of moving device. The present description also includes a servo motor  80 , and a ball screw, however, the present invention is not limited to any particular type of drive source or force transferring device. 
   Although a few preferred embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.