Abstract:
An apparatus and a method for individually bagging bundles into stretchable open bags. The apparatus comprises a bag stretching structure about which a bag can be turned inside out for wrapping an underlying bundle in response to continuous downward movement of the bag stretching structure once the closed end of the bag opposite the open end thereof has engaged the top surface of the bundle.

Description:
RELATED APPLICATIONS 
     The present application claims priority on Canadian Patent Application No. 2,340,838 filed on Mar. 15, 2001 and on U.S. Provisional Patent Application No. 60/305,162 filed Jul. 16, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus and a method for bagging goods, such as bundles of wood, in stretchable bags. 
     2. Description of the Prior Art 
     Some wood products, such as rectangular bundles of lumber strips, need to be protected from the environment and stored in a way such as to preserve an appropriate degree of humidity and prevent UV rays from damaging the wood. 
     In the past, various bagging apparatus have been developed to load agricultural products into stretchable plastic tube. However, there is still a need for a new apparatus and method for providing effective and convenient bagging or sheathing of rigid wood products into stretchable bags or the like. 
     SUMMARY OF THE INVENTION 
     It is therefore an aim of the present invention to provide an apparatus and a method for wrapping material, such as bundles, into stretchable bags. 
     It is also an aim of the present invention to provide such an apparatus which is of sturdy construction. 
     It is a further aim of the present invention to provide such an apparatus which is reliable and which offers convenience in use. 
     Therefore, in accordance with the present invention, there is provided an apparatus for bagging material into a stretchable bag having an open end. The apparatus comprises a movable bag stretching structure displaceable between a first position for receiving the bag and a second position for holding the bag in a stretched state. The apparatus further includes at least two bag gripping members for turning the bag inside out over the movable bag stretching structure while the same is in its first position. An actuator is provided for displacing the bag stretching structure towards a facing side of the material while the bag is held in a stretched state thereon such that a continuous movement of the bag stretching structure about the material causes the bag to be gradually inverted on the material after the bag has engaged the facing side of the material. 
     In accordance with a further general aspect of the present invention, there is provided a method for wrapping a bundle into a stretchable bag having an open end and an opposed closed end, comprising the steps of: fitting the bag about a stretching structure, stretching the bag by operation of said stretching structure, and wrapping the bundle into the taut bag by inverting the bag onto the bundle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof, and in which: 
     FIG. 1 is a side elevation view of a bagging apparatus in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is a top plan view of the bagging apparatus of FIG. 1; 
     FIG. 3 is a cross-sectional view of a pair of side-by-side belt conveyors forming part of the apparatus of FIG. 1; 
     FIG. 4 is a schematic side elevation view of a stretching column forming part of a stretching and bagging unit of the apparatus of FIG. 1; 
     FIG. 5 is a schematic front elevation view of the stretching column of FIG. 4; 
     FIG. 6 is a schematic top plan view of the stretching column of FIG. 4; 
     FIG. 7 is a simplified front end elevation view of a pair of stretching column, one of which is equipped with a tip folding system in accordance with one aspect of the present invention; and 
     FIG. 8 is a simplified side elevation view of one of the stretching column and associated folding system of FIG.  7 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now referring to the drawings, and in particular to FIG. 1, a bagging apparatus  10  suited for sheathing or bagging a substantially rectangular or square bundle B of wood within a resilient sheath S will be described. 
     The sheath S is provided in the form of an elongated web of flexible, stretchable, resilient plastic material that is folded in two about a central longitudinal axis thereof and then rolled on a supply reel  12  with the fold line of the sheath S forming the upper edge of the roll of material. 
     The bagging apparatus  10  generally comprises a supply unit  14 , a sealing and cutting unit  16  and a stretching and bagging unit  18 . 
     The supply unit  14  comprises a loading platform  20  pivotally mounted at  22  to a rectangular framework  24  supporting the sealing and cutting unit  16  and the stretching and bagging unit  18  of the apparatus  10 . A hydraulic cylinder  26  extends between the framework  24  and the loading platform  20  to pivot the latter between a horizontal functional position and a vertical loading position (both positions being shown in solid lines in FIG.  1 ). A motorized turntable  28  is mounted on the platform  20 . An axle  30  extends at right angles from the turntable  28  for receiving the supply reel  12 . A pivot arm  32  is pivotally mounted to a frame structure  33  mounted to the platform  20  for receiving the free distal end of the axle  30  once the supply reel  12  has been loaded thereon. A lock pin  34  is provided to lock the pivot arm  32  to the axle  30 , thereby preventing axial withdrawal of the reel  12  from the axle  30 . 
     To load a new supply reel on the axle  30 , the platform  20  is first pivoted from its horizontal position to the vertical position thereof, as indicated by arrow  35  in FIG. 1; second, the lock pin  34  is removed and the pivot arm  32  is manually pivoted away from the axle  30 ; and finally, the reel  12  is slidably fitted on the axle  30 . Thereafter, the pivot arm  32  is pivoted back in engagement with the axle  30  and locked thereto, and the cylinder  26  is extended to pivot the platform  20  back to its horizontal position. A brake  36  (FIG. 2) is provided for engaging the turntable  28  to prevent the sheath S from being unrolled from the supply reel  12  when required or desired. 
     As shown in FIGS. 1 and 2, the sheath S is directed from the supply reel  12  to a first pre-stretching motorized roller  38  mounted on a vertical shaft  40  which is, in turn, mounted on the loading platform  20 . A second pre-stretching motorized roller  42  (FIG. 2) is provided on the framework  24  for receiving the sheath S from the first pre-stretching roller  38 . The first and second pre-stretching rollers  38  and  42  cooperate to pre-stretch the sheath S so as to subsequently facilitate the full stretching thereof in the stretching and bagging unit  18 . Two or more set of pre-stretching rollers driven at increased speed from one set to the next can be provided for pre-stretching the sheath S before the same is transferred to the stretching and bagging unit  18 . 
     From the second pre-stretching roller  42 , the sheath S is directed between a pair of indexing motorized vertical rollers  44  and  46  supported by the framework  24 . As seen in FIG. 2, the roller  46  is mounted to a support  47 . A pneumatic cylinder  45  is provided for linearly reciprocating the support  47  and, thus, the roller  46  away from and towards the roller  44 . In use, the roller  46  is initially displaced away from the roller  44  to an open position for receiving the sheath S and then displaced back against the sheath S and the roller  44  to a closed functional position for drawing the sheath S forward into the apparatus  10 . 
     The sheath S is transferred from the indexing rollers  44  and  46  to an overhead transport rail system  48  mounted to the framework  24 . As seen in FIG. 2, the overhead transport rail system  48  includes a pair of side-by-side axially extending belt conveyors  50  and  52  adapted to receive therebetween the upper end of the sheath S (i.e. the end with the fold line). The belt conveyors  50  and  52  each include an endless flexible belt  54  extending over a pair of axially spaced-apart rollers  56  and  58 . The roller  58  of each pair is motorized to drive the associated belt  54 . The belt  54  of the conveyor  52  slides between rollers  56  and  58  on a movable plate  60  (FIG. 3) displaceable towards, and away from, the other belt conveyor  50  so as to close or open the gap defined between the conveyors  50  and  52 . A pair of pneumatic cylinders  62  (FIG. 3) are provided for displacing the plate  60 . When the overhead transport system  48  is used to transport the sheath S forwardly through the apparatus  10 , the cylinders  62  are extended and when it is desired to release the sheath S, the cylinders  62  are retracted so as to increase the gap between the belts  54  of the conveyors  50  and  52 . 
     As seen in FIG. 1, the rollers  56  and  58  of the conveyors  50  and  52  are mounted on respective shafts  64 . The position of the rollers  56  and  58  is adjustable along the shafts  64  for allowing the apparatus  10  to be used in conjunction with sheaths of different sizes. 
     As shown in FIGS. 1 and 2, the sealing and cutting unit  16  is mounted to the framework  24  between the indexing rollers  44  and the overhead transport rail system  48 . The sealing and cutting unit  16  generally comprises a vertically displaceable cutting blade (not shown) and a pair of vertically extending elongated heating elements  66  facing each other from opposite sides of the central axis of the apparatus  10 . The heating elements  66  are positioned to receive the sheath S therebetween and are displaceable towards, and away from, each other between a closed operative position and an open idle position. Pneumatic cylinders, such as those illustrated at  68  in FIG. 1, are provided for displacing the heating elements  66  between the open and closed positions thereof. Each heating element can be provided with a pair of heating bands (not shown) to simultaneously seal the sheath S on each side of the cut. It is also understood that a linear actuator (not shown) is provided for displacing the cutting blade in upward and downward directions to effect cutting of a desired length of sheath S. 
     Referring to FIGS. 1 and 2, it can be seen that the stretching/bagging unit  18  comprises an upstream pair of stretching columns  70  and an identical pair of downstream stretching columns  72 . The upstream stretching columns  70  are slidably mounted in linear front transversal rails  74  (FIG. 1) and are displaceable towards, and away from, each other by means of a pair of cylinders  76  (FIG. 2) mounted in an end-to-end relationship between the upstream stretching columns  70 . Likewise, the downstream stretching columns  72  are slidably mounted in linear transversal rails  78  and are displaceable towards, and away from, each other by means of a pair of cylinders  80  mounted in an end-to-end relationship between the downstream stretching columns  72 . The transversal rails  74  form part of a front carriage  82  mounted in linear axially extending rails  84  provided on top of the framework  24 . Similarly, the transversal rails  78  form part of a rear carriage  86  mounted in linear axially extending rails  88  provided on top of the framework  24 . First and second ball screws  90  and  92  are respectively engaged with first and second ball nuts  94  and  96  for respectively displacing the front and rear carriages  82  and  86  along the longitudinal axis of the apparatus  10 , as illustrated in FIG.  1 . The first and second ball screws  90  and  92  are driven by respective electric rotary motors  98  and  100 . Accordingly, the ball screws  90  and  92  are operable to displace the pair of upstream stretching columns  70  and the pair of downstream stretching columns  72  towards, and away from, each other along the longitudinal axis of the apparatus  10 . 
     As seen in FIGS. 4,  5  and  6 , each column  70 / 72  comprises on opposed sides thereof a pair of lower suction members  102  for opening the sheath S after the same has been cut and sealed so as to form a bag open at its bottom (FIG.  5 ). Each lower suction member  102  includes a hollow perforated planar head  104  which is connected to a pneumatic cylinder  105  (FIG. 6) for allowing the same to be linearly displaced relative to the associated column  70 / 72  towards and away from the sheath S. A vacuum pump (not shown) or the like is provided for drawing air into the suction members  102  through the perforated heads  104  thereof. Each column  70 / 72  is further provided with an upper suction member  106  having a perforated face plate  108  through which air can be drawn by operation of the vacuum pump. As opposed to the perforated heads  104  of the lower suction members  102 , which are located on the inner side of the columns  7 Q and  72 , the perforated face plates  108  of the upper suction members  106  are located on the outer side of the columns  70  and  72  so as to retain the bag when the same has been turned inside out over the columns  70  and  72 , as will explained hereinbelow. 
     Each stretching column  70 / 72  is further provided on opposed lateral sides thereof with a pair of rotary gripping arms  110 . As seen in FIG. 5, each rotary gripping arm  110  includes an arcuate arm segment  112  which is  180  degrees pivotable relative to the associated column  70 / 72  for allowing the bag to be turned inside out over the columns  70  and  72 . Each rotary gripping arm  110  is linearly displaceable in a vertical slot  114  defined in the associated column  70 / 72 . An actuator  116 , such as a rodless TOL-O-MATIC actuator, can be provided within each column  70 / 72  for linearly displacing the associated pair of rotary gripping arms  110 . 
     Each rotary gripping arm  110  is provided with a stationary gripping finger  118  and a pivotable gripping finger  120 . A pneumatic cylinder  122  is provided for displacing the pivotable gripping finger  120  between an open position and a closed position wherein the pivotable gripping finger  120  is urged against the associated stationary finger  118  to clamp a side of the bag at the mouth thereof. 
     Finally, as shown in FIG. 4, each column  70 / 72  is provided with a vertically movable sheath lowering plate  124 . The sheath lowering plate  124  is mounted in a pair of vertical rails  126  provided on an outer side of the associated column  70 / 72 . The sheath lowering plate  124  is displaced along the rails  126  in opposed ascending and descending directions by means of a ball screw  128  engaged with a ball nut  130  secured to the sheath lowering plate  124 . An electric motor  132  is provided for driving the ball screw  128  and, thus, cause displacement of the plate  124 . 
     It is also contemplated to equip one of the front columns  70  and one of the rear columns  72  with a tip folding system  150  (FIGS. 7 and 8) to fold down or press down the triangular tip  152  formed by the seams at the upstream and downstream ends of the sheath or bag. As exemplified in connection with the columns  70 , each tip folding system  150  is operational to place the tip  152  of the associated seam of the bag against the corresponding face of the bundle B to be bagged so that when the bag is inverted onto the bundle B, the tip  152  of the seam is folded into the outer surface of the bag itself, as opposed of extending upwardly from one end of the bundle B. 
     Each tip folding system  150  generally includes an arcuate arm  154  slidable between an extended position (shown in broken lines in FIG. 7) and a retracted position within a guiding structure  156  provided on an inner facing side of the associated column  70 / 72 . The arm  154  is displaced by operation of a pneumatic cylinder  158  mounted within the column  70 / 72 . According to one embodiment of the present invention, the pneumatic cylinder  158  has a 36 inches stroke. By extending the pneumatic cylinder  158  while the bag is stretched and turned inside out over the columns  70  and  72 , the arm  154  is lowered so as to place and maintain the tip  152  of the seam against the associated end face of the bundle B, as illustrated in FIG.  7 . The subsequent lowering of the vertically movable sheath lowering plate  124  will cause the bag to be inverted onto the bundle B with the tip  152  covered by or folded into the exterior surface of the bag so as to form a pleat in the bag at each end of the bagged bundle. After the folding operation, the pleat formed by the tip  152  can be sealed or otherwise secured in place to prevent the same from being unfolded while the bagged bundle is transported from one location to another. 
     As seen in FIG. 1, the bundle B is supported in position within the framework  24  underneath the overhead transport system  48  by a roller conveyor  134 . It is understood that an entry conveyor (not shown) and an exit conveyor (not shown) are also provided at opposed ends of the apparatus  10 . 
     In operation, a length of sheath S is drawn into the apparatus  10  from the supply reel  12  between the indexing rollers  44  and the overhead transport rail system  48  above the bundle B so as to determine the length of sheath S to be cut in accordance with the bundle length. Then, the sheath S is cut and sealed to form the closed downstream end of a bag for the underlying bundle B and a closed upstream end for the next bundle to be bagged. It is understood that the upstream end of the sheath S has been previously sealed during a previous bagging cycle. After, the sheath S has been cut and sealed, the overhead transport rail system  48  is powered back to displace the so-formed bottom open bag directly above the underlying bundle B. 
     Then, the cylinders  76  and  80  are operated to displace the columns  70  and  72  towards the sides of the bag and the mouth thereof is opened by extending the lower suction members  102  next to the opposed external sides of the bag and by subsequently operating the vacuum pump to cause the bottom end of the bag to be drawn against the perforated heads  104  of the lower suction members  102 , as illustrated in FIG.  5 . Once the mouth of the bag has been opened by the bottom suction members  102 , the rotary gripping arms  110  are pivoted, as indicated by arrow  136  in FIG. 5, and the gripping fingers  118  and  120  thereof become closed against the sides of the bag. The suction at the perforated heads  104  of the lower suction members  102  is then stopped and the overhead transport rail system  48  is displaced to an open position thereof in order to release the upper end of the bag. 
     Thereafter, the bag is turned inside out over the four columns  70  and  72  by imparting a rotation of  180  degrees to the rotary gripping arms  110  in the direction indicated by arrow  138  in FIG.  5 . The bag is then fitted about the columns  70  and  72  by linearly displacing the rotary gripping arms  110  to the upper end of the associated slot  114 , as shown in FIG.  5 . Air is then drawn into the upper suction members  106  to retain the bag and the gripping fingers  118  and  120  of all the gripping arms  110  are opened to release the bag therefrom. The open mouth of the bag is then at the upper end thereof. 
     Once the bag has been properly inverted and fitted about the columns  70  and  72 , the cylinders  76  and  80  are actuated to stretch the bag in the transversal direction of the bundle B and the framework  24 . Then, the ball screws  90  and  92  are operated to stretch the bag in the longitudinal direction of the bundle B. At this point, the vacuum pump can be shut down. The cylinders  158  are then extended to lower the arms  150  to position the tips  152  of the seams at the downstream and upstream ends of the bag against the corresponding faces of the bundle B, as illustrated in FIG.  7 . The taut open end bag is then lowered onto the underlying bundle by actuating the ball screws  128  so as to downwardly displace the sheath lowering plates  124  and cause the bag to be inverted on the bundle B as the top surface of the bundle B engages the bottom closed end of the bag opposite the open end thereof. Once, the bag has been fitted on the bundle B with the tips  152  of the seams folded inwards, the arms  154  are retracted and the plates  124  are displaced upwardly. The stretching columns  70  and  72  are then returned to their initial positions. Thereafter, the bagged bundle is displaced to a storage location and another bundle may be bagged as per the cycle described hereinabove.