Patent Publication Number: US-6658821-B2

Title: Bag loading method and assembly for a bag filling station

Description:
RELATED APPLICATIONS 
     The present application is a divisional of U.S. patent application Ser. No. 09/798,449 filed Mar. 2, 2001, and is hereby incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to devices for opening, filling, and sealing plastic bags and other packaging. More particularly, the invention relates to automated devices that can produce an air-tight seal when packaging bulky products. 
     BACKGROUND OF THE INVENTION 
     Bag opening and filling devices have been developed for a wide variety of applications. Typically, these devices include one or more mechanisms for selecting a single bag from a stack of flattened, usually folded bags, and holding the selected bag open for filling. Prior-art devices commonly include a wicket that holds a stack of bags to be filled. Bags are torn from the wicket and opened prior to filling. Once the bag is opened, a pusher mechanism loads the product into the bag and a sealing mechanism seals the bag after the product has been loaded. 
     In modern packaging applications many different types of products are loaded into bags. It is difficult to obtain an air-tight or hermetic seal using available automated sealing equipment when packaging bulky products, such as diapers, sanitary napkins, paper napkins, and similar products. Fortunately, it is unnecessary to package these types of products in air-tight bags. However, there are applications that require hermetic sealing of the bag. 
     Packaging medical supplies is one such application. Hermetic sealing is required to ensure that the medical supplies are not contaminated after they are packaged and sealed in the bags. Attempts to automate the packaging and sealing of bulky medical supplies have been unsuccessful due to the problems associated with placing a bulky object in a flat bag and then attempting to bring the open edges of the bag together for sealing. The open edges wrinkle, which prevents the formation of a proper seal along the entire length of the bag opening. Consequently, bulky medical supplies are packaged and sealed by hand to ensure that a hermetic seal is produced. Manual packaging and sealing has several deficiencies. It is cumbersome, time-consuming, and vulnerable to human error. 
     SUMMARY OF THE INVENTION 
     Thus, there is a need for an automated packaging device that can be used to package medical supplies and other products in bags and to hermetically seal the bags. In addition, it would be beneficial if such a machine could monitor the quality of the seal. Further still, there is a need for a device where a relatively large number of bags can be loaded or otherwise provided to the packaging device so that product can be packaged at a relatively high rate without the need for replenishing the supply of bags at a similarly high rate. 
     In one embodiment, the invention provides an automated bag filling station or packaging device capable of rapidly packaging medical supplies and other bulky products in bags and sealing the bags in an air-tight manner. The packaging device includes a bag feeder for a bag filling device. The bag feeder includes a bag cartridge tray for holding at least one bag and a conveyor assembly positioned above the bag cartridge tray. The conveyor assembly is movable between a first position, where the conveyor assembly engages a bag, and a second position, where the conveyor assembly is inclined with respect to the bag cartridge tray. 
     In one aspect of the invention, the conveyor assembly includes first and second rollers, a body portion between the first and second rollers, at least one vacuum generator communicating with the body portion for providing vacuum to the conveyor assembly, and an endless belt encircling portions of the rollers and the body portion. The endless belt engages the bag from the bag cartridge tray when the conveyor assembly is in the first position, and moves the bag to a position where the bag can be opened and filled when the conveyor assembly is in the second position. 
     Preferably, the body portion includes an upper cavity communicating with an upper surface and a lower cavity communicating with a lower surface. Each of the upper and lower surfaces includes apertures communicating with the respective upper and lower cavities such that vacuum in the upper cavity communicates with the apertures in the upper surface and vacuum in the lower cavity communicates with the apertures in the lower surface. Further preferably, at least one of the rollers communicates with a vacuum generator to supply a vacuum to the outer surface of the roller. 
     In another embodiment, the invention provides a method of loading a bag into a loading station of an automated packaging device. The method includes providing a stack of bags and providing a conveyor assembly adjacent the stack of bags. The conveyor assembly is movable between a first, bag engaging position and a second, bag loading position, and has an endless conveyor capable of moving a bag to different locations on the conveyor assembly. The method further includes engaging a bag from the stack of bags when the conveyor assembly is in the first position, moving the conveyor assembly to the second position, actuating the endless conveyor to move the bag away from the stack of bags and into a loading position, and actuating the endless conveyor to move the bag into the loading station. 
     In one aspect of the invention, engaging the bag is accomplished using a vacuum. In another aspect, moving the conveyor assembly to the second position and actuating the endless conveyor to move the bag away from the stack of bags and into a loading position occur substantially simultaneously. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of an automated packaging device embodying the invention. 
     FIGS. 1 a  and  1   b  are top views of the package loading assembly in various operating states. 
     FIG. 2 is an enlarged side view showing one of the support members of FIG. 1 in the package sealing position. 
     FIG. 3 is an enlarged side view showing the bag loading assembly of the device of FIG.  1 . 
     FIGS. 4-6 are side views of the conveyor assembly portion of the bag loading assembly of FIG. 3 shown in various operational states. 
     FIG. 7 is a partially cut away view of the conveyor assembly taken along line  7 — 7  in FIG.  4 . 
     FIG. 8 is a front view showing a loading station, a bag manipulating assembly, and a bag welding assembly of the device of FIG.  1 . 
     FIG. 9 is an enlarged front view of the loading station and the bag manipulating assembly shown with a bag opened for receiving a package. 
     FIG. 10 is a perspective view of the loading station, the bag manipulating assembly, and a portion of a bag loading assembly loading a package into the opened bag. 
     FIG. 11 is an alternative gripper arrangement that can be used with the bag manipulating assembly. 
     FIG. 12 is a sectional view of the welding jaws showing an alternative pressure sensor configuration. 
     FIGS. 13-20 sequentially illustrate, in cross-section from the side, the opening, closing, and sealing of the bag. 
     FIGS. 21-28 sequentially illustrate, from the front, the opening, closing, and sealing of the bag. 
     FIG. 29 is a sealed bag containing a package. 
     FIGS. 30-32 illustrate an alternative spreader plate arrangement for the bag manipulating assembly. 
    
    
     Before the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of multiple embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
     DETAILED DESCRIPTION 
     A bag filling station  50  of one embodiment is shown in FIG.  1 . The bag filling station  50  includes a frame  54  (only partially shown) that supports the bag filling station  50 . The frame  54  can also support protective walls (not shown) positioned around the bag filling station  50 , as is commonly understood. 
     The bag filling station  50  includes a loading station  58  positioned within the frame  54 , a package loading assembly  62  coupled to the frame  54  adjacent the loading station  58 , a bag loading assembly  66  coupled to the frame  54  adjacent the loading station  58 , a bag manipulating assembly  70  coupled to the frame  54  adjacent the loading station  58 , and a bag welding assembly  74  (see FIG. 8) coupled to the frame  54  adjacent the loading station  58 . For purposes of description only, the bag filling station  50  can be defined in terms of a front  78 , adjacent the package loading assembly  62 , a rear  82  adjacent the bag loading assembly  66 , a right side  86 , and a left side  90  (see FIG.  8 ). A longitudinal axis  94  (see FIGS. 1,  1   a ,  1   b ,  9 , and  10 ) extends from the front  78  to the rear  82  through the loading station  58 . 
     As seen in FIGS. 1,  1   a ,  1   b , and  10 , the package loading assembly  62  includes a package conveyor assembly  98  capable of transporting packages  102  to the loading station  58 . The package conveyor assembly  98  includes a conveyor table  106  supported by support legs  110  (see FIG.  1 ). The conveyor table  106  includes an endless conveyor belt  114  (see FIG. 10) driven by a drive device  118  (see FIG.  1 ). A suitable conveyor table  106  is available from Dorner Manufacturing of Hartland, Wis. The drive device  118  can be any suitable device capable of moving the conveyor belt  114 , such as an electric motor. 
     The package conveyor assembly  98  also includes a pair of pusher arm assemblies  122  movably coupled to the conveyor table  106 . The pusher arm assemblies  122  are substantially identical, and only one will be described. As seen in FIG. 1, the pusher arm assembly  122  includes a slide  126  mounted on a support member  130  for reciprocating linear movement in the direction of the longitudinal axis  94 . The linear movement of the pusher arm assembly  122  is driven by any linear actuator (not shown) such as a hydraulic or pneumatic actuator, a rack and pinion system, and the like, or can be driven by the drive device  118 . 
     The pusher arm assembly  122  also includes a pusher arm  134  having a pushing end  138  for pushing a package  102  into the loading station  58 . As best seen in FIG. 1 a , the pusher arm  134  is movable between a retracted position P R  (shown in solid lines in FIG. 1 a ), where a package  102  can be advanced on the conveyor table  106  between the two pusher arms  134  toward the loading station  58 , and an extended position P E  (shown in phantom lines in FIG. 1 a ), where the two pusher arms  134  overlie the conveyor table  106 . As shown in FIG. 1 b , when in the extended position, the pusher arms move linearly from the position P 1  (shown in solid lines in FIG. 1 b ), to the position P 2  (shown in phantom lines in FIG. 1 b ) so that the pushing ends  138  can push the package  102  into the loading station  58 . 
     Any suitable method of causing the movement of the pusher arms  134  between the retracted and extended positions can be used, including hydraulic or pneumatic actuators, rack and pinion systems, and the like. While the package conveyor assembly  98  preferably includes two pusher arm assemblies  122 , it is understood that only one pusher arm assembly  122  could be used. Pusher arm assemblies having other configurations are also contemplated, including those shown in U.S. Pat. No. 5,799,465 incorporated by reference herein. 
     The package conveyor assembly  98  also preferably includes a sensor  142  (see FIG. 1) that senses the presence of a package  102  on the conveyor table  106  when the package  102  is adjacent the loading station  58 . The sensor  142 , which can be in the form of an optical sensor, a limit switch, or the like, communicates with the pusher arm assemblies  122  so that the pusher arm assemblies  122  are activated to push the package  102  when the package  102  is in position adjacent the loading station  58 . 
     The package conveyor assembly  98  can also include guide rails  144  (see FIGS. 1 a  and  1   b ) on either side of the conveyor table  106  extending substantially parallel to the longitudinal axis  94  to help guide the package  102 . The guide rails  144  can be adjustable to accommodate packages  102  of varying heights and widths. 
     As seen in FIGS.  1  and  3 - 7 , the bag loading assembly  66  includes a bag feeder or bag conveyor assembly  146  capable of transporting a bag  150  to the loading station  58  for receiving a package  102 . The bags have an open end for receiving the package  102 . The bag conveyor assembly  146  includes a conveyor assembly  154  supported by support legs  158 . As best seen in FIGS. 3-7, the conveyor assembly  154  includes a conveyor table  160  comprised of a body portion  162 , a drive roller  166 , a follower roller  170 , a pair of tensioner rollers  174 , an endless conveyor belt  178  encircling portions of the body portion  162  and the rollers  166 ,  170 , and  174 , and side supports  180  (only one is shown in FIG.  3 ). 
     The body portion  162  includes an upper cavity  182  and a lower cavity  186  separated by a wall  190 . The wall  190  separates the cavities  182 ,  186  such that there is substantially no fluid communication between the cavities  182 ,  186 . Upper and lower inlet ports  194  and  198 , respectively (see FIG.  3 ), provide fluid communication to the cavities  182 ,  186  as will be described below. The body portion  162  further includes a top surface  202  having elongated apertures  206  communicating between the top surface  202  and the upper cavity  182 . The body portion  162  also includes a bottom surface  210  having elongated apertures  214  that are substantially identical to the apertures  206  and that communicate between the bottom surface  210  and the lower cavity  186 . The body portion  162  has an overall width W (see FIG.  7 ). 
     Vacuum from a vacuum generator  218  (see FIG. 1) is applied to the body portion  162  through separate supply hoses  222  and  223 . The upper supply hose  222  provides vacuum to the upper cavity  182  through the upper inlet port  194 . The lower supply hose  223  provides vacuum to the lower cavity  186  through the lower inlet port  198 . Of course, two separate vacuum generators could be used. 
     The elongated apertures  206 ,  214  supply vacuum to the respective top and bottom surfaces  202 ,  210  over a working width W′ (see FIG.  7 ). The working width W′ of vacuum at the top and bottom surfaces  202 ,  210  is adjustable to accommodate the width of the bags  150  being used. In one embodiment, as shown in FIG. 7, a working width adjustment mechanism  226  is used to selectively block and unblock all or portions of some of the apertures  206 ,  214 . To accomplish this, a pair of slide plates  230  (only the top slide plate is shown in FIG. 7) is moved to block and unblock the apertures,  206 ,  214 . The slide plates  230  can be actuated manually or automatically. 
     The drive roller  166  is spaced from one end of the body portion  162 , preferably in the rearward direction, and is supported for rotation between the side supports  180 . A drive device  234  drives the drive roller  166 . In one embodiment, the drive device  234  is an electric motor, and more preferably an electric motor that is programmed to actuate the drive roller  166  through a predetermined number of revolutions in either direction as will be described below. Alternatively, a standard electric motor could be used in conjunction with a sensing device (not shown) such as an optical sensor, a limit switch, or the like. 
     The follower roller  170  is spaced from the end of the body portion  162  opposite the drive roller  166 , and is also supported for rotation between the side supports  180 . The follower roller  170  preferably includes a cavity  238  that communicates with apertures  242  formed in the surface of the follower roller  170 . A vacuum is applied to the follower roller  170  as shown schematically in FIG.  7 . The vacuum generator  218  or a separate vacuum generator (not shown) is used to supply vacuum to the follower roller  170 . It should be understood, however, that the follower roller  170  need not be configured to provide vacuum. 
     The endless conveyor belt  178  encircles the rollers  166 ,  170  such that there is always a portion of the conveyor belt  178  engaging both the top surface  202  and the bottom surface  210 . The tensioner rollers  174  are supported for rotation between the side supports  180  as shown in FIG. 3, and at least one of the tensioner rollers  174  is movable to adjust the tension in the conveyor belt  178  as is understood. Of course other arrangements can be used to adjust the tension of the conveyor belt  178 . 
     As seen in FIG. 7, the conveyor belt  178  includes a plurality of transverse apertures  246  that provide communication between the outer surface of the conveyor belt  178  and the respective top and bottom surfaces  202 ,  210  so that the vacuum supplied from the vacuum generator  218  to the body portion  162  can communicate with the outer surface of the conveyor belt  178 . In the illustrated embodiment, each transverse aperture  246  communicates with two apertures  206  when adjacent the top surface  202  and two apertures  214  when adjacent the bottom surface  210 . The transverse apertures  246  also communicate with the apertures  242  in the follower roller  170  so that a vacuum is also applied to the outer surface of the conveyor belt  178  as the conveyor belt  178  passes over the follower roller  170 . 
     Although it is preferable to use vacuum, the conveyor table  160  need not be configured to supply vacuum to the conveyor belt  178 . Rather, the conveyor table  160  could use other suitable techniques, such as static attraction, to engage and manipulate the bags  150  in the manner discussed below. 
     The conveyor table  160  is pivotable about the axis of rotation of the drive roller  166  between a first, substantially horizontal position P H  (as shown in solid lines in FIGS.  1  and  3 ), and a second, inclined position P I  (as shown in phantom lines in FIGS.  1  and  3 ). The purpose of this movement will be described below. A drive device  250  (see FIG. 1) is connected via linkage members  254  to one or both of the side supports  180  adjacent the follower roller  170  as shown. Activation of the drive device  250  moves the linkage members  254  to move the conveyor table  160  between the first and second positions P H , P I . Of course, other methods of moving the conveyor table  160  between the first and second positions, such as the use of actuators, rack and pinion systems, and the like, are also contemplated. 
     As best seen in FIGS. 1 and 3, the bag conveyor assembly  146  also includes a bag holder or cartridge tray assembly  258  underneath the conveyor table  160  for holding a stack of bags  150 . A bag tray  262  is supported by the support legs  158  and receives a stack of bags  150  which are positioned between guide walls  266  (only two are shown in FIGS.  1  and  3 ). To facilitate replacing the stack of bags  150  in the bag tray  262 , the bag tray  262  is preferably mounted on rollers  270  (see FIG. 3) and can be rolled out from underneath the conveyor table  160 . 
     As best seen in FIG. 3, a lifting plate  274  inside the bag tray  262  is connected to a lifting mechanism  278  that is fixed to one of the support legs  158 . The lifting mechanism can be an actuator, a rack and pinion system, or the like. As will be described below, the lifting mechanism  278  is actuated to move the lifting plate  274  to raise or lower the stack of bags  150  with respect to the bottom of the bag tray  262 . 
     The conveyor assembly  154  can also include a take-off conveyor  282  (see FIGS. 3-7) for receiving filled bags  150  as they exit the conveyor table  160 . The take-off conveyor  282  acts as a bridge between the conveyor table  160  and a permanent conveyor (not shown) that transports the filled bags  150  to an off-loading point. Of course, the take-off conveyor  282  can be eliminated if the permanent conveyor is arranged adjacent the drive roller  166  of the conveyor table  160 . 
     The loading station  58  is positioned between the package loading assembly  62  and the bag loading assembly  66  and is best seen in FIGS.  1  and  8 - 10 . The frame  54  includes a substantially rectangular support section  286  (see FIGS.  1  and  8 ) which substantially surrounds the loading station  58  and which supports the bag manipulating assembly  70  and the bag welding assembly  74 . Upper and lower transverse shafts  290  and  294 , respectively, are supported for rotation by the support section  286  and are coupled together via linkages  298 . A drive device  302  (see FIG. 8) is coupled to the lower shaft  294  and selectively rotates the lower shaft  294  in either direction. When the lower shaft  294  is rotated, the linkages  298  cause rotation of the upper shaft  290 . 
     A pair of upper support members or struts  306  are mounted to the upper shaft  290  and connect the upper shaft  290  to an upper jaw support member  310  (see FIG.  8 ). The upper jaw support member  310  is movably supported on substantially vertical guide rails  314  within the frame support section  286 . Rotation of the upper shaft  290  causes vertical movement of the upper jaw support member  310 , as will be described below. 
     Likewise, a pair of lower support members or struts  318  are mounted on the lower shaft  294  and connect the lower shaft  294  to a lower jaw support member  322 . The lower jaw support member  322  is movably supported on the guide rails  314 . Rotation of the lower shaft  294  causes vertical movement of the lower jaw support member  322 , as will be described below. Each of the lower struts  318  has mounted thereon a pressure measurement device or sensor  324 . The pressure sensor  324  is preferably a load cell. For reasons to be explained in more detail below, the lower struts  318  are sized so that as the lower jaw support member  322  reaches its uppermost vertical limit, the struts  318  are oriented substantially vertically as shown in FIG.  2 . If the range of motion of the lower jaw support member  322  is varied for different applications, the struts  318  can be adjusted so that the struts  318  will always be substantially vertical when the lower jaw support member  322  reaches the uppermost vertical limit. 
     The upper and lower jaw support members  310 ,  322  support portions of the bag manipulating assembly  70  and the bag welding assembly  74 . As best seen in FIG. 9, the lower jaw support member  322  supports a lower welding jaw  326 , which will be described in more detail below. A plurality of suction cup assemblies  330  are mounted in spaced relation on a front face of the lower welding jaw  326 . Each suction cup assembly  330  is connected to a vacuum supply and can selectively apply suction via a suction cup  334 . As will be described below, the suction cup assemblies  330  are used to engage an open end of the bag  150 . 
     A pair of rotary actuators  338  are also mounted on the lower jaw support member  322 . Each rotary actuator includes a pin  342  that can be both rotated and translated with respect to the housing of the rotary actuator  338 , as is understood. A spreader plate  346  is mounted on the pin  342  of each rotary actuator  338 . The purpose of the spreader plate  346  will be described below. Together, the suction cup assemblies  330 , the rotary actuators  338 , and the spreader plates  346  define a lower bag spreader assembly  348 . 
     The upper jaw support member  310  supports an upper welding jaw  350  and a substantially identical upper bag spreader assembly  352  in opposing relation to the lower bag spreader assembly  348 . The upper bag spreader assembly  352  includes suction cup assemblies  354  having suction cups  358 , and a pair of rotary actuators  362 . Each rotary actuator  362  has a pin  366  and a spreader plate  370  mounted on the pin  366 . 
     Additionally, the upper jaw support member  310  includes a pair of cam members  374  adjustably mounted to mounting plates  378 . The cam members  374  are substantially identical and only one will be described. Each cam member  374  is fastened to one mounting plate  378  via upper and lower fasteners  382  and  383 . The upper fastener  382  is received in a slot  386  in the cam member  374  such that the cam member  374  is pivotally adjustable about the lower fastener  383 . The cam member  374  further includes a cam surface  390  corresponding to an edge of the cam member  374 . Adjustment of the cam member  374  changes the angle of the cam surface  390 . The cam surface  390  can include an optional dwell point  394  (shown in phantom in FIG.  9 ), which will be described below. 
     The cam members  374  cooperate with another portion of the bag manipulating assembly  70 . As best seen in FIGS. 8 and 9, a support beam  398  is fixedly supported between the guide rails  314 . Unlike the upper and lower jaw support members  310 ,  322 , the support beam  398  is not free to move vertically along the guide rails  314 . A pair of gripper arm assemblies  402  (see FIG. 9) are mounted on the support beam  398  in spaced-apart, opposing relation. The gripper arm assemblies  402  are substantially identical, and only one will be described in detail. 
     Each gripper arm assembly  402  includes a bracket member  406  having a base portion  410  and an arm portion  414 . A gripper arm  418  is pivotally connected to the base portion  410  at pivot point  422 . A cam follower  426  is mounted to the gripper arm  418  and engages the cam surface  390 . In the illustrated embodiment, the cam follower  426  is a roller. A linear actuator or gripper  430  is mounted on the end of the gripper arm  418  for gripping the side edges of a bag  150 , as will be described below. The gripper  430  is preferably a pneumatically-actuated, parallel gripper. 
     With continuing reference to FIG. 9, as the upper jaw support member  310  moves downwardly, the cam followers  426  roll on the cam surfaces  390  and the gripper arms  418  pivot about the pivot points  422  in a plane substantially normal to the longitudinal axis  94 . Downward movement of the upper jaw support member  310  causes the gripper arms  418  and the grippers  430 , to move away from one another. As the upper jaw support member  310  moves upwardly, the gripper arms  418  and the grippers  430  move back toward each other in a plane substantially normal to the longitudinal axis  94 . The dwell points  394  in the cam surfaces  390  are designed to change the cam surfaces  390  so that the pivot arms  418  will not pivot during certain points of the operation of the bag filling station  50 , as will be described below. 
     On both gripper arm assemblies  402 , a linear actuator  434  is connected between the arm portion  414  and the gripper arm  418 . Together, the linear actuators  434  are operable to pivot the gripper arms  418  even further away from one another than would otherwise occur via the normal movement of the cam followers  426  along the cam surfaces  390 . The linear actuators  434  are preferably short-stroke pneumatic actuators. As will be described below, the linear actuators  434  are preferably actuated just prior to the sealing of the bag  150  when the upper jaw support member  310  is at its lowermost vertical limit. 
     FIG. 11 illustrates a pair of alternative gripper assemblies  438  that can be used in place of the gripper arm assemblies  402 . Instead of the cam action used to pivot the gripper arm assemblies  402 , the alternative gripper assemblies  438  are fixedly mounted to the opposing vertical members of the frame support section  286 , and are linearly actuated to move the grippers  430  toward or away from each other. The gripper assemblies  438  are substantially identical and include back-to-back cylinders  442 ,  443  having respective rods  446 ,  447 . 
     The rod  446  is connected to a sliding portion  450  which slides on a guide rail  454 . Actuation of the cylinder  442  moves the rod  446  and causes movement of the sliding portion  450 . The rod  447  is connected to a body portion  456  that is fixed with respect to the frame support section  286 . Actuation of the cylinder  443  causes the cylinders  442  and  443  to move with respect to the body portion  456 , thereby causing movement of the sliding portion  450 . The gripper  430  is mounted on the sliding portion  450  so that actuation of either of the cylinders  442 ,  443  causes the grippers  430  to move toward or away from one another. 
     The components of the bag manipulating assembly  70  operate to receive the bag  150  from the bag loading assembly  66 , open the open end of a bag  150  so that the package  102  can be inserted, and close the open end of the bag  150  once the package  102  has been inserted. The bag  150  is closed in a manner that is conducive to obtaining a quality seal of the open end of the bag  150 . The bag  150  is under the control of the bag manipulating assembly  70  from the time it is received to the time it is removed from the loading station  58 . 
     The bag welding assembly  74  is used to weld or seal the open end of the bag  150  after the package  102  has been inserted. The welding assembly  74  includes the upper and lower welding jaws  350 ,  326  and the associated hardware which are available from TOSS Machine Components Inc. of Nazareth, Pa. As seen in FIG. 13, in one embodiment, each of the welding jaws  326 ,  350  includes a body portion  458 , a fiberglass strip  462 , a silicon strip  466 , a teflon strip  470 , and a weld wire  474 . A layer of teflon tape  478  surrounds the working ends of the welding jaws  326 ,  350 . Of course, welding could be accomplished with only one of the welding jaws  326 ,  350  having a weld wire  474 . 
     The upper welding jaw  350  can also include a cutter assembly  482  that trims off a portion of the bag  150  after the open end has been sealed. The cutter assembly  482  can include a knife edge  486  that extends to trim the bag  150  when the welding jaws  326 ,  350  are closed. Of course, other cutter assembly configurations can be used. For example, a welding jaw having a sealing wire that simultaneously seals and cuts the bag  150  could also be used. 
     The welding assembly  74  also includes the pressure measurement devices  324  mounted on the lower struts  318 . The pressure measurement devices are used to measure the pressure between the welding jaws  326 ,  350  while the bag  150  is sealed. Recall that as the lower welding jaw  326  reaches its uppermost vertical limit (i.e., the position where the welding takes place), the lower struts  318  are substantially vertical. This orientation promotes accurate measuring of the welding pressure because the pressure measurement devices  324  are in axial alignment with the forces exerted on the lower welding jaw  326  by the upper welding jaw  350 . 
     FIG. 12 illustrates an alternative arrangement for the pressure measuring device. In FIG. 12, a pressure measurement device  490  (i.e., a load cell or the like) is mounted in a recess in the upper welding jaw  350 . A contact disk  494  is mounted in a recess in the lower welding jaw  326 . Multiple sets of devices  490  and disks  494  can be spaced along the length of the welding jaws  326 ,  350  as desired. 
     Regardless of the pressure measuring arrangement used, the pressure measuring devices  324 ,  490  are used to monitor the quality of the seal that is created by the welding jaws  326 ,  350 , as will be described below. Verifying the formation of a quality seal without human intervention, and being able to document and record the process for future reference is an advantage of the bag filling station  50 . The bags  150  are sealed using heat to melt the open end of the bag  150  together, as is understood. At least three components are important to achieve a good seal: pressure, temperature, and time. The bag filling station  50  monitors these three components so that the quality of the seal can be validated, which is especially important when packaging medical devices. 
     Time is the easiest to control, and refers to the time the pressure and heat are applied during the sealing process. Temperature is more difficult to control and measure, but suitable products are available. Pressure is applied using the drive device  302 , such as an electric motor. Controlling the pressure entails controlling the current in the electric motor. Alternatively, pressure could be controlled via an air-cylinder (not shown). Pressure is measured using the pressure measurement devices  324 , as described below. 
     During the sealing process, the weld wires  474  are heated to a temperature set by a controller or processor  502 . The processor  502  is preferably a programmable logic control device and can have a video display  506 . The temperature is held for a predetermined time dictated by the processor  502 . The actual temperature of the weld wires  474  is monitored and temperature signals are sent to the processor  502  via signal lines  510 . The actual temperature is compared to predetermined temperature settings. 
     When the heat command is removed, the welding seam is allowed to cool and pressure is applied for a time specified by the processor  502 . As seen in FIG. 8, the pressure measuring devices  324  are linked to the processor  502  via lines  512 . The processor  502  analyzes the signals from the pressure measurement devices  324  and determines the actual welding pressure applied. In one embodiment, the measured pressure, heat, and time values are displayed on the video display  506  and are compared to a predetermined values to determine the quality of the seal. Additionally, two or more pressure measurements (corresponding to the number of pressure measurement devices  324  or  490  used) are compared to one another to determine the consistency of the seal along the length of the welding jaws  326 ,  350 . With this approach, inconsistent or incomplete sealing caused by debris between the welding jaws  326 ,  350  or wrinkles in the bag  150  can be detected. 
     The processor  502  reads and records the pressure and temperature data at a predetermined sampling rate that allows the process to be validated. Each seal has data associated with it that the seal was heated to a certain temperature and that a certain pressure was maintained for a certain time. If any of the data indicates that improper sealing conditions were present, the sealed bag is rejected. While not shown, the bag filling station  50  can also include a marking device that can be used to catalog the sealed bags by placing some form of indicating feature (i.e., a serial number, a bar code, or the like) on the bags that is linked to the weld data. When the bags are marked with an indicating feature, the seal quality of any bag can be verified at a later time. 
     The operation of the bag filling station  50  will now be described. The bags  150  are first stacked in the bag tray  262  so that the open ends are to the right as viewed in FIG.  3 . The bag tray  262  is then slid into place underneath the conveyor table  160 . With the conveyor table  160  in the substantially horizontal first position P H , the lifting mechanism  278  is actuated to lift the stack of bags  150  toward the bottom surface  210  of the body portion  162 . As seen in FIG. 4, when vacuum is applied to the lower cavity  186 , the top bag  150  on the stack of bags is engaged by the conveyor belt  178  due to the vacuum communication between the apertures  214  and the transverse apertures  246 . Once the top bag  150  is engaged with the conveyor belt  178 , the lifting mechanism  278  is lowered to lower the stack of bags  150  away from the bottom surface  210 . 
     Next, the drive device  234  indexes the drive roller  166  such that the bag  150  moves with the conveyor belt  178  as shown in FIG.  5 . Vacuum is applied to the follower roller  170  to hold the bag  150  in engagement with the conveyor belt  178  as the bag  150  passes over the follower roller  170 . At approximately the same time, the drive device  250  drives the linkage members  254  to move the conveyor table  160  from the first position P H  to the second, inclined position P I . As the bag  150  approaches the top surface  202 , vacuum is applied to the upper cavity  182  to maintain the engagement between the conveyor belt  178  and the bag  150 . At about the same time, the vacuum is turned off in the lower cavity  186 . Once the conveyor belt  178  has traveled a predetermined distance (as gauged by the programmable motor or the sensing device), and the bag  150  is on top of the conveyor table  160 , the drive device  234  reverses direction to load the open end of the bag  150  into the loading station  58  as shown in FIG.  6 . 
     FIGS. 13-20 and  21 - 28  illustrate (from the side and the front, respectively) the sequential operation of the bag manipulating assembly  70  and the bag welding assembly  74  once the bag  150  is loaded into the loading station  58 . As seen in FIGS. 13 and 21, the bag is moved into the loading station  58  and the side edges of the bag  150  pass through the open grippers  430 . The open end of the bag  150  is oriented substantially horizontally in the loading station  58  as shown. The upper and lower welding jaws  350 ,  326  (and therefore the upper and lower bag spreader assemblies  348 ,  352 ) are slightly opened to provide clearance for the bag  150 . In this position, the cam followers  426  are positioned in or near the dwell point  394 . 
     Next, as seen in FIGS. 14 and 22, the grippers  430  close, thereby securely clamping the opposing side edges of the bag  150  to maintain control over the bag  150  at all times during the packaging operation. Additionally, the welding jaws  326 ,  350  close so that the suction cups  334 ,  358  approach the open end of the bag  150  from both sides. Due to the presence of the dwell points  394 , the grippers  430  do not move toward each other as the jaws  326 ,  350  close. Vacuum is applied to the suction cups  334 ,  358  so that the suction cups  334 ,  358  engage both sides of the open end of the bag  150 . 
     As seen in FIGS. 15 and 23, the welding jaws  326 ,  350  then open slightly. Because the suction cups  334 ,  358  have a suction grip on the top and bottom of the open end of the bag  150 , the bag  150  opens slightly in response to the opening of the welding jaws  326 ,  350 . Again, due to the dwell point  394 , the grippers  430  do not move toward each other. The grippers  430  (shown schematically in FIG. 15) remain closed to keep a secure grip on the side edges of the bag  150 . 
     Next, as seen in FIGS. 16 and 24, the rotary actuators  338 ,  362  are actuated so that the spreader plates  346 ,  370  rotate into the open end of the bag  150 . The pins  342 ,  366  of the rotary actuators  338 ,  362  also retract to draw the spreader plates  346 ,  370  closer to the respective suction cups  334 ,  358 . Meanwhile, the suction is still being applied to the bag  150  by the suction cups  334 ,  358 . The grippers  430  remain closed. 
     At this point, it is worth noting that other spreader plate arrangements can also be used to open the bag. FIGS. 30-32 illustrate alternative upper and lower bag spreader assemblies  514  and  518 , respectively. Instead of the rotary actuators  338 ,  362  having the rotating and translating spreader plates  346 ,  370 , the alternative upper and lower bag spreader assemblies  514  and  518  include respective upper and lower pivoting bag spreader plates  522  and  526 . Respective actuators  530  and  534  cause the pivoting bag spreader plates  522  and  526  to pivot into and out of the open end of the bag  150  as is sequentially shown in FIGS. 31 and 32. 
     Returning to FIGS. 17 and 25, the welding jaws  326 ,  350  are opened wider so that the open end of the bag  150  is opened widely enough to receive a package  102 . Both the suction cups  334 ,  358  and the spreader plates  346 ,  370  aid in opening the bag  150 . As best seen in FIG. 9, when the upper welding jaw  350  is moved upwardly to open the bag  150 , the gripper arms  418  pivot inwardly toward each other in response to movement of the cam members  374 . The inward pivoting of the gripper arms  418  moves the grippers  430  toward each other and facilitates spreading the open end of the bag  150  apart. The grippers  430  remain closed to hold the side edges of the bag  150 . 
     Sometime before the package  102  is pushed into the bag  150 , the conveyor table  160  of the bag loading assembly  66  is returned to the first, substantially horizontal position P H  (see FIGS. 1 and 4) so that the package  102  can be pushed into the bag  150  without being obstructed by the follower roller  170 . Returning the conveyor table  160  to the horizontal position also prepares the bag loading assembly  66  for picking up the next bag  150  from the stack. 
     At this point, the bag  150  is ready to receive a package  102 . The package  102  is placed on the conveyor table  106  (see FIG. 1) and the drive device  118  drives the conveyor belt  114  to move the package  102  toward the loading station  58 . The pusher arms  134  are in the retracted position P R  (see FIG. 1 a ) to allow the package  102  to pass by. When the sensor  142  detects the package  102 , the conveyor belt  114  stops and the pusher arms  134  move to the extended position P E  to overlie the conveyor table  106 . The pusher arm assemblies  122  then move linearly toward the waiting package  102  so that the pushing ends  138  engage the package  102  (see FIGS. 1 b  and  10 ) and push the package  102  into the bag  150  (see FIGS.  18  and  26 ). The pusher arms  134  are then withdrawn from the bag  150  and returned to the retracted position P R  in anticipation of the next packaging cycle. 
     With the package  102  inside the bag  150 , the bag  150  is sealed. As seen in FIGS. 19 and 27, the welding jaws  326 ,  350  close so that the open end of the bag  150  closes. Just prior to closing, the spreader plates  346 ,  370  rotate out of the bag  150 . The suction is turned off at the suction cups  334 ,  358 . As the upper welding jaw  350  moves downwardly, the gripper arms  418  pivot outwardly, away from each other. Since the grippers  430  are still closed on the side edges of the bag  150 , the outward movement of the gripper arms  418  acts to stretch the bag  150 , thereby helping to flatten the open end of the bag  150  in preparation for sealing. 
     To ensure that the open end of the bag  150  closes substantially without any wrinkling caused by the bulky package  150  inside the bag, the linear actuators  434  connected to the gripper arms  418  (see FIGS. 8 and 9) pull the gripper arms  418  even further outwardly, away from each other. This additional outward movement of the grippers  430  stretches the side edges of the bag  150  apart even further to completely flatten the open end of the bag  150  and to substantially remove any wrinkles that could cause inconsistent or incomplete sealing. 
     Electricity is applied to the weld wires  474  to heat seal the open end of the bag  150 , as is understood. The processor  502  monitors the weld temperature, pressure, and time as described above to monitor the quality of the seal obtained. 
     Either during, or just after welding, the cutter assembly  482  is activated to trim the bag  150  as shown in FIG.  20 . As shown in FIG. 28, the trimmed bag pieces  538  are removed from the loading station  58  using a vacuum tube  542 . The vacuum tube  542  is a tube positioned adjacent the loading station  58  where the trimmed bag pieces  538  are located. Vacuum supplied to the vacuum tube  542  extracts the trimmed bag pieces  538  and deposits them in a waste receptacle (not shown). Of course, other methods of removing the trimmed bag pieces  538  can be used. Alternatively, the sealed bag  150  need not be trimmed at all. 
     With the bag  150  packed and sealed, the grippers  430  are opened to release the side edges of the bag  150  and the conveyor belt  178  is activated to move the sealed bag  150  out of the loading station  58  and to the take-off conveyor  282  (see FIGS.  7  and  8 ). As seen in FIGS. 7 and 8, the next packaging cycle is underway and the next bag  150  from the stack is concurrently being engaged and moved into the loading position by the conveyor belt  178 . 
     While not shown in the figures, the follower roller  170  can also be adapted to remove the air from inside the packed and sealed bag  150  if vacuum packing is desired. Alternatively, vacuum packing could occur at a later time on a different machine. 
     FIG. 29 illustrates a packed and sealed bag  150 . The sealed area extends across the width of the bag  150  and is generally designated by the reference numeral  546 . 
     Various features of the invention are set forth in the following claims.