Abstract:
A vibrating table assembly for an apparatus for filling and weighing bulk bags comprises a bag support table, vibrating means for vibrating the bag support table, and a lifting device for raising an lowering the bag support table, the lifting device being located below the bag support table. Preferably, the lifting device comprises a convoluted air bellows. Location of the lifting device below the table overcomes problems encountered with known bag filling apparatus where the bag support table and the lifting mechanism are connected to the frame of the apparatus.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to apparatus for filling and weighing bulk bags, and particularly relates to vibrating table assemblies for use in such apparatus.  
       BACKGROUND OF THE INVENTION  
       [0002]     Efficient filling and weighing of bulk bags (also known as flexible intermediate bulk containers) is performed with an apparatus on which a bulk bag is suspended by loops above a bag support table. During filling of the bag, the bag bottom is partly supported by the support table, which typically has a top portion shaped like a flattened, truncated pyramid. A pair of unbalanced counter-rotating motors are located inside the support table to vibrate and compact the contents of the bag as it is being filled.  
         [0003]     The bag support table is brought into contact with the bulk bag either by lowering the bag or raising the support table. Two types of apparatus in which the support table can be raised and lowered are disclosed in U.S. Pat. Nos. 4,718,464 and 5,336,853. In U.S. Pat. No. 4,718,464, the support table is raised and lowered by a piston and cylinder device attached to the frame of the bag filling apparatus. In U.S. Pat. No. 5,336,853, the support table is raised and lowered by a screw and collar system incorporated into the frame.  
         [0004]     To ensure that a bulk bag is filled with the correct amount of material, it may be weighed several times during the filling cycle. In order to accurately weigh the bulk bag, it must be separated from the bag support table. Each time the bulk bag is weighed, the motors in the support table are allowed to wind down, and the bag support table is lowered. As the motors wind down, they lose their synchronization and generate significant vibrational forces on the bag support table. With the support table attached to the frame of the apparatus, these vibrations are effectively absorbed.  
         [0005]     However, attachment of the bag support table and the lifting mechanism to the frame prevents the bag support table from being used for retrofit applications, for example to be incorporated into an older style bag filling apparatus not having a bag support table. Therefore, there is a need for a self-contained bag support table which does not rely on the frame of the bag filling apparatus for support or for vibration damping.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention overcomes the above limitations of the prior art by providing a vibrating table assembly for a bag filling apparatus. The vibrating table assembly according to the invention is a self-contained unit comprising a bag support table of similar or identical shape to the tables shown in the prior art, vibrating means for vibrating the bag support table, a lifting device for raising and lowering the bag support table, with the lifting device being located below the bag support table, and at least one resilient connector through which the lifting device is connected to the bag support table. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a side elevational view of a preferred table assembly according to the present invention, with the bag support table at its upper height limit;  
         [0008]      FIG. 2  is a front elevational view of the table assembly of  FIG. 1 , with the bag support table at its upper height limit;  
         [0009]      FIG. 3  is a front elevational view of the table assembly of  FIG. 1 , with the bag support table at its lower height limit; and  
         [0010]      FIG. 4  is a side elevation showing the table assembly of  FIG. 1  mounted to the frame of a bag filling apparatus. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0011]     FIGS.  1  to  3  illustrate a preferred table assembly  10  according to the present invention.  
         [0012]     Table assembly  10  comprises a bag support table  12 , a vibrating device  14  for vibrating the bag support table  12 , a lifting device  16  for raising and lowering the bag support table  12  and at least one resilient connector  17  through which the bag support table  12  and the lifting device  16  are connected. As shown in the drawings, the lifting device  16  is located below the bag support table  12 .  
         [0013]     The bag support table  12  and vibrating device  14  are similar to those described in prior U.S. Pat. Nos. 4,718,464 and 5,336,853, mentioned above. Specifically, the bag support table  12  is rectangular, preferably square, in plan view, having a rectangular upper surface  18 , four vertical side surfaces  20 , and four sloped side surfaces  22  connecting the vertical side surfaces  20  and the upper surface  18 . The side surfaces  20 ,  22  extend outwardly and downwardly from the upper surface  18  to a lower edge  19  of the table  12 . The table  12  has four corners  21  at which the side surfaces  20  converge with one another and with the lower edge  19 . It will be appreciated that the table need not have the rectangular shape shown in the drawings, but may be of any other suitable shape, including circular in plan view.  
         [0014]     The vibrating device  14  comprises one or more vibrating motors, and preferably comprises two unbalanced counter-rotating motors  24  which are at least partially enclosed in a hollow space  23  defined by the upper surface  18  and the side surfaces  20 ,  22 , and are preferably mounted inside the bag support table  12  by a mounting bracket  26 .  
         [0015]     As shown in the drawings, the lifting device  16  is located centrally below the bag support table  12 , such that a central vertical axis  27  of the table assembly  10  extends through the centre of the bag support table  12  and the centre of the lifting device  16 . Locating the lifting device  16  centrally below the bag support table  12  assists in absorbing side loads caused by vibrations generated during winding down of the motors  24 .  
         [0016]     The connection between the lifting device  16  and the bag support table  12  is preferably made through a rectangular, preferably square, mounting plate  28  having an upper surface  30  and a lower surface  32 . As shown, the bag support table  12  is mounted on the upper surface  30  of mounting plate  28 , with the lifting device  16  being attached to the lower surface  32 .  
         [0017]     In order to absorb vibration caused by motors  24 , the bag support table  12  is preferably connected to the mounting plate  28  in a manner which will dampen vibration of the motors  24 . In the preferred embodiment shown in the drawings, the bag support table  12  and mounting plate  28  are connected through one or more resilient connectors  17  which, in the preferred embodiment shown in the drawings, comprise a plurality of spring supports  34 . As shown in the drawings, four such spring supports  34  are preferably provided, each of which is secured at its lower end to a respective corner of the mounting plate  28 . The upper ends of the spring supports  34  are secured to an elongate, L-shaped bracket  36  ( FIG. 2 ) which forms part of the bag support table and which is secured by welding or other suitable means to the inside of the bag support table  12 . Each spring support  34  comprises a coil spring  38  secured at its upper and lower ends by spring retainers  40  and bolts  42  which may preferably be threaded into tapped openings (not shown) in the mounting plate  28  and L-shaped bracket  36 .  
         [0018]     Although the preferred resilient connectors described and shown in this application are spring supports comprising axially-extending coil springs positioned at the corners of the support table, it will be appreciated that resilient connectors other than spring supports can be used. For example, the resilient connectors may comprise elastomeric supports which are comprised of a resilient polymeric material such as rubber, the elastomeric supports being mounted between the lifting device and the bag support table. It will also be appreciated that the table assembly according to the invention could include more or fewer resilient connectors than shown in the drawings, depending on the shape of the table and the degree of vibration damping required. For example, a resilient connector may be centrally located between the lifting device and the support table.  
         [0019]     As shown in the drawings, the lifting device  16  preferably comprises a convoluted air bellows  44  having a top plate  46  and bottom plate  48  made of metal, and an expandable central portion  50  between the top plate  46  and bottom plate  48 . Preferably, the central portion  50  is made of an elastomeric material such as rubber, and can be inflated by a pressurized gas such as air. The top plate is preferably provided with a gas inlet/outlet  52  which is preferably connected by a flexible hose  54  to a source of pressurized gas (not shown).  
         [0020]     The top plate  46  is secured to the lower surface  32  of mounting plate  28 , preferably by bolts  55 , with the gas inlet/outlet  52  of the air bellows  44  extending through an aperture  56  in the mounting plate  28 .  
         [0021]     The table assembly  10  further comprises a rectangular base plate  58  having an upper surface  60  on which the bottom plate  48  of air bellows  44  is mounted, preferably by bolts  62  which are countersunk into the base plate  58 .  
         [0022]     The inventors have found that the use of a convoluted air bellows is particularly preferred over other types of lifting devices, as it permits the table assembly  10  to be very compact. For example, with the air bellows  44  in its fully collapsed condition, shown in  FIG. 3 , the entire table assembly  10  preferably has a height of about 17 inches, which is comparable to that of prior art table assemblies in which the raising and lowering means are contained in the frame of the bag filling apparatus. Such a low profile may not be possible with other conventional lifting devices. Furthermore, the entire table assembly can fit within the footprint of the filling and weighing apparatus.  
         [0023]     The convoluted air bellows is also preferred since it is effective to absorb side loads which result when the bag support table  12  is lowered during winding down of the motors  24 . Such side loading could cause other types of lifting devices to bind.  
         [0024]     In the preferred embodiment shown in the drawings, the air bellows is a triple convoluted air bellows, comprising three inflatable sections  64 .  
         [0025]     In order to prevent deformation of the mounting plate  28  when the bag support table  12  is raised against the bottom of a bulk bag, the lower surface  32  of mounting plate  28  is preferably provided with a peripheral, downwardly extending skirt  66 .  
         [0026]     The table assembly  10  is also provided with stop members for preventing downward movement of the bag support table  12  beyond a lower height limit ( FIG. 3 ), and for preventing upward movement of the bag support table  12  beyond an upper height limit ( FIGS. 1 and 2 ).  
         [0027]     The assembly  10  includes a plurality of lower stop members which are preferably mounted on the base plate  58  or the mounting plate  28 , and which limit downward movement of the mounting plate  28  relative to the base plate  58 . In the preferred embodiment shown in the drawings, there are four lower stop members, each in the form of a hollow sleeve  68  extending downwardly from the lower surface  32  of the mounting plate  28 . Each sleeve  68  has an outwardly extending base flange  69  by which it is secured to the mounting plate  28  by welding or the like, as well as a lower surface  70 . The length of each sleeve  68  is substantially the same as the height of the air bellows  44  in its collapsed condition, as shown  FIG. 3 . With air bellows  44  in this condition, the lower surface  70  of each sleeve  68  abuts the upper surface  60  of mounting plate  58 . With the air bellows  44  collapsed as shown in  FIG. 3 , the bag support table  12  is at its lower height limit, preferably having a height, measured from the base plate  58  to the upper surface  18  of support table  12 , of about 17 inches.  
         [0028]     As best seen in  FIGS. 2 and 3 , table assembly  10  is provided with a pair of upper stop members  72 . Each upper stop member  72  comprises an elongate member  74  which may preferably comprise a bolt. The elongate member  74  has an enlarged upper end  76  which may preferably comprise a bolt head or other suitable enlargement. The lower end  78  of elongate member  74  is attached to the upper surface  60  of base plate  58 . In the preferred embodiment, the bolt comprising elongate member  74  is provided with threads at its lower end  78 . The threads engage the threads of a nut  80  which is secured to the upper surface  60  of base plate  58 .  
         [0029]     Attached to the lower surface  32  of mounting plate  28  are a pair of brackets  82 , each of which comprises a U-shaped channel having a lower portion  84  which is substantially horizontal, and a pair of substantially vertical sides  86  which are connected to the mounting plate  28 . The lower portion  84  of bracket  82  has an aperture  88  through which the elongate member  74  extends. The aperture  88  is sized to closely receive the portion of elongate member  74  which is intermediate the ends  76 ,  78 , and has an area which is less than the area of enlarged upper end  76  of elongate member  74 , such that when the bag support table  12  is at its upper height limit (shown in  FIGS. 1 and 2 ) the enlarged upper end  76  of elongate member  74  abuts the lower portion  84  of bracket  82  and is located between the lower portion  84  of bracket  82  and the lower surface  32  of the mounting plate  28 .  
         [0030]     As seen in  FIG. 3 , the brackets  82  preferably also function as lower stop members, with the lower portion  84  abutting the upper surface  60  of base plate  58  when the air bellows  44  is in its collapsed condition. In order to accomplish this, the aperture  88  in the lower portion  84  of bracket  82  preferably has a diameter sufficient to accommodate nut  80 .  
         [0031]     In the preferred embodiment shown in the drawings, a pair of upper stop members  72  are provided. Each of the upper stop member  72  is located adjacent a short edge of base plate  58  ( FIG. 2 ) and preferably spaced centrally between the longer sides of base plate  58  ( FIG. 1 ).  
         [0032]     It will be appreciated that the table assembly  10  can be provided with more or fewer upper stop members  72  than shown in the drawings. However, at least two such stop members  72  are preferred in order to prevent binding of the elongate member  74  due to side loading which occurs during winding down of motors  24 .  
         [0033]     As the air bellows  44  collapses under the weight of the bag support table  12 , the mounting plate  28  and bag support table  12  move downwardly relative to the upper end  76  of elongate member  74 . Therefore, the mounting plate  28  is provided with apertures  92  ( FIG. 2 ) which are located directly above each upper stop member  72  to permit the elongate member  74  to pass through the mounting plate  28  as shown in  FIG. 3 . Similarly, the L-shaped brackets  36  are provided with apertures  94  ( FIG. 2 ) through which the upper stop member  72  can pass. Preferably, with the bag support table  12  at its lower height limit as shown in  FIG. 3 , the upper end  76  of elongate member  74  is received between L-shaped bracket  36  and the side surfaces  20 ,  22  of bag support table.  
         [0034]     Although the upper stop members  72  assist in guiding the vertical movement of the support table  12 , the assembly  10  is preferably provided with one or more additional guide members to keep the vertical axis  27  aligned with the vertical during raising and lowering the support table  12 . In the preferred embodiment shown in the drawings, the vertical guide members comprise four vertically extending rods  96 , each having an upper end  98  and a lower end  100 , with the lower end  100  being secured to the base plate  58  by countersunk screws  102 . With the bag support table  12  at its upper height limit, the upper end  98  of each rod  96  is received in one of the sleeves  68  comprising the lower stop member. As the support table  12  is lowered, the upper end  98  of each rod  96  passes through an aperture  104  in the mounting plate  28 . When the support table  12  is at its lower height limit, as shown in  FIG. 3 , the upper end of each rod  96  is received just below the upper surface  18  of the support table  12 , between the vibrating motors  24  and one of the L-shaped brackets  36 .  
         [0035]     The table assembly  10  is preferably either mounted to the floor below the bag filling apparatus or to the frame of the filling apparatus. For floor mounting, the base plate  58  is secured to the floor by fasteners such as bolts or the like, preferably at or near its four corners. One possible arrangement for mounting a bag filling apparatus  100  is illustrated in  FIG. 4 , which shows only two vertical frame members  102  and a horizontal cross member  104  of the apparatus  100 . It will be appreciated that the apparatus  100  partially illustrated in  FIG. 4  preferably has four vertical members  102  forming a rectangular frame, with two cross members  104  extending between the vertical members  102  in spaced, parallel relation, as in U.S. Pat. Nos. 4,718,464 and 5,336,853. In the embodiment shown in  FIG. 4 , the table assembly is mounted to the horizontal frame members, with the base plate  58  being secured at or near its corners to the horizontal frame members  104 . The base plate  58  is preferably secured by fasteners such as bolts  106  or the like, with only the heads of bolts  106  being visible in  FIG. 4 . As the frame structure shown in  FIG. 4  is common to many existing bag filling apparatus, the mounting arrangement shown in  FIG. 4  permits the table assembly  10  to be incorporated into an existing apparatus with minimal modification.  
         [0036]     Although the invention has been described in connection with certain preferred embodiments, it is not intended to be limited thereto. Rather, the invention is intended to include all embodiments which may fall within the scope of the following claims.