Abstract:
A lifting and stabilizing mechanism for an apparatus such as a bag elevator assembly for an automated filling machine having a stationary frame and a generally horizontal carriage mounted for vertical movement relative to the frame. The carriage is carried on a plurality of geared belts which each criss-cross the frame in an opposing &#34;Z&#34; configuration, and are alternately wrapped over and under opposed drive wheels and tensioning wheels rotatably mounted on the carriage. The opposing belts maintain the carriage in its horizontal orientation, and the drive wheels are rotated to provide the lift force for controllably raising and lowering the carriage. The drive belts are attached to and extend along vertical brace members of the frame using one of various clamping assemblies, and the vertical alignment of the carriage is augmented by a pin and channel guide assembly. Exact vertical linear registration or displacement of the carriage is accomplished by monitoring the revolutions of the drive wheels, drive axle, or drive motor, and comparing those revolutions to a predetermined chart or formula relating revolutions to linear displacement.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to lifting and stabilizing apparatuses for vertical auger type bag filling machines, and particularly to a mechanism employing opposing Z-belts. 
     Lifting and stabilizing mechanisms for automated bag filling equipment, alternately referred to as bag elevator assemblies, are know to the art. Existing lifting and stabilizing mechanisms usually comprise vertical tracks on which carriages travel, the tracks having beveled edges which engage grooved guide wheels on the carriage, or vice versa. The carriages are generally lifted and lowered using a combination of one or more drive gears and chains, servos, or dual acting power cylinders. A representative example of such a mechanism as described above may be seen in U.S. Pat. No. 4,944,334 and its related applications. 
     These lifting and stabilizing mechanisms are used to control the raising and lowering of bag handling mechanisms, including bag gripping and hanging mechanisms for mounting and holding a bag on a fill spout, and mechanisms for moving that bag relative to a fill tube or fill spout during filling by a filling machine such as a vertical auger bag filler. These lifting and stabilizing mechanisms may also be utilized to carry bag tamping or settling mechanisms, net weigh scales, and additional equipment or controls. 
     In order to ensure proper vertical alignment and uniform horizontal orientation, the configuration of conventional lifting and stabilizing mechanisms generally require very heavy and bulky assemblies. The increase in size and weight of the mechanisms requires proportionately higher capacity drives in order to controllably lift and lower the mechanisms at the speeds required by automated fill systems, and proportionately larger areas in which the machines are placed. In a system for filling fifteen 100 lbs. bags per minute with a powdered product, for example, the lifting and stabilizing mechanism might account for ten to twenty times the weight of the filled bag. Consequently, the mechanism is far more difficult to tune, requires heavier duty and more expensive components to endure prolonged usage, requires more complicated controls and regulating mechanisms to ensure accuracy and uniformity over extended periods, and generally consume more energy and are less efficient than lighter and smaller mechanisms. The size of these mechanisms can also affect the ability to integrate other devices, such as bag infeed or hanging mechanisms, release and conveyor assemblies, weigh scales, vacuum systems or de-aeration mechanisms, and safety or control devices. 
     BRIEF SUMMARY OF THE INVENTION 
     It is one therefore object of this invention to design a lifting and stabilizing mechanism for use with an automated bag filling machine such as a vetical auger which provides extremely accurate and uniform vertical alignment and horizontal orientation for a bag handling carriage or similar system. 
     It is another object of this invention to design the above lifting and stabilizing mechanism such that it can be operated at extremely high speed while maintaining both accurate vertical linear registration and a precise incremental control over the rate of vertical movement in the upward and downward directions. 
     It is an additional object of this invention to design the above lifting and stabilizing mechanism such that it is smaller and lighter weight than conventional assemblies, thereby consuming less energy in operation, and permitting a wider range of operating environments and configurations. 
     It is a related object of this invention to minimize and integrate the operational functions of the above lifting and stabilizing mechanism to require fewer regulating mechanisms, controls, and drive mechanisms. 
     It is yet another object of this invention to design the above lifting and stabilizing mechanism to minimize wear on components, and to provide a system wherein worn components can be easily detected and replaced without disassembling the apparatus or removing the apparatus from the associated automated filling machine. 
     Briefly described, the lifting and stabilizing mechanism of this invention incorporates a stationary frame and a generally horizontal carriage mounted for vertical movement relative to the frame. The carriage is carried on a plurality of geared belts which each criss-cross the frame in an opposing &#34;Z&#34; configuration, and are alternately wrapped over and under opposed drive wheels and tensioning wheels mounted on the carriage. The opposing belts maintain the carriage in its horizontal orientation, and the drive wheels are rotated to provide the lift force for controllably raising and lowering the carriage. The drive belts are attached to the frame using one of various clamping assemblies, and the vertical alignment of the carriage is augmented by a pin and channel guide assembly. Exact vertical linear registration o displacement of the carriage frame is accomplished by monitoring the revolutions of the drive wheels, drive axle, or drive motor, and comparing those revolutions to a predetermined chart or formula relating revolutions to linear displacement. One example of this lifting and stabilizing mechanism permits vertically registered movement of a five hundred pound carriage and bag hanging assembly over a five foot lift path in less than three quarters of a second. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view from above of the Z-belt lifting and stabilizing mechanism of this invention; 
     FIG. 2 is a side elevation view of the Z-belt mechanism of FIG. 1; 
     FIG. 3 is is a perspective view from below of the Z-belt mechanism of FIG. 1; 
     FIG. 4 is a perspective detail view of the pin and channel guide of the Z-belt mechanism of FIG. 1; 
     FIG. 5 is a front elevation view of one drive chain clamping assembly of the Z-belt mechanism of FIG. 1; 
     FIG. 6 is a partial cross section view of the drive chain clamping assembly of FIG. 5 taken from line 6--6 in FIG. 5; 
     FIG. 6a is a partial cross section view of an alternate embodiment of the drive chain clamping assembly of FIG. 5 taken from line 6--6 in FIG. 5 showing the drive belt orientation reversed; 
     FIG. 7 is a side view of a section of the drive chain of the Z-belt mechanism of FIG. 1; 
     FIG. 8 is a partial cross section view of an alternate embodiment of the drive chain clamping assembly of FIG. 5 taken from line 6--6 in FIG. 5; 
     FIG. 9 is a top partial cross section view of the alternate embodiment of the drive chain clamping assembly of FIG. 8 taken from line 9--9 in FIG. 8; 
     FIG. 10 is an exploded view of a tensioning wheel assembly of the Z-belt mechanism of FIG. 1; 
     FIG. 11 is a side cross section view of a drive wheel assembly of the Z-belt mechanism of FIG. 1, taken from the viewpoint of line 11--11 in FIG. 10; 
     FIG. 12 is a partial perspective view of an alternate embodiment of the Z-belt lifting and stabilizing mechanism of this invention in which two drive wheels and two tensioning wheels are disposed on one side of the carriage frame, with the drive wheels on opposing ends of the carriage frame; 
     FIG. 13 is a partial perspective view of an alternate embodiment of the Z-belt lifting and stabilizing mechanism of this invention in which two drive wheels and two tensioning wheels are disposed on one side of the carriage frame; 
     FIG. 14 is a partial perspective view of an alternate embodiment of the Z-belt lifting and stabilizing mechanism of this invention in which one drive wheel and one tensioning wheel is disposed on each side of the carriage frame, with the drive wheels on opposing ends of the carriage frame; and 
     FIG. 15 is a partial perspective view of an alternate embodiment of the Z-belt lifting and stabilizing mechanism of this invention in which one drive wheel and one tensioning wheel is disposed on each side of the carriage frame, with the drive wheels disposed proximate to the same end of the carriage frame. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The Z-belt lifting and stabilizing mechanism of this invention is shown in FIGS. 1-15 and referenced generally therein by the numeral 10. 
     Referring particularly to FIG. 1, the Z-belt mechanism 10 is shown mounted within a frame 12 which also supports any conventional type automated bag filling machine having a hopper or auger bowl 14 from which a fill tube 16 depends. The Z-belt mechanism 10 carries the components of an automated bag gripping and hanging mechanism 18 including a clam-jaw type fill spout 20, bag hanging arms 22 having bag gripping members 24, as well as the appropriate type of bag 26 for use with the product to be filled by the automated bag filling machine. 
     Representative examples of the components of such an automated bag filling machine, including the auger bowl 14, fill tube 16, spout 20, bag hanging arms 22, and bag gripping members 24, may are shown in U.S. Pat. Nos. 4,322,932; 4,432,186; 4,612,965; and the above referenced 4,944,334. 
     Referring again to FIG. 1, the frame 12 is seen to consist of a plurality of vertical beams 28 and horizontal beams 30. Mounted within the frame 12 in generally vertical alignment are four generally vertical brace members 32, each brace member 32 being disposed in one of the four corners of the frame 12 such that each of two pairs of the brace members 32 face one other and are spaced apart on opposing sides of the auger bowl 14 and spout 16. 
     The automated bag gripping and hanging mechanism 18 is disposed beneath the spout 16 with the lower spout shroud 20 being attached to and carried on a carriage frame 34, the carriage frame 34 having a pair of spaced-apart side members 36 and cross members 38 extending between and connecting the side members 36. The carriage frame 34 is positioned so as to be generally centered between the front and back pair of brace members 32 as shown in FIG. 1, the opposing ends of each of the side members 36 extending to a point closely proximate to the inner surface 40 of each of the left and right side pair of brace members 32. In some applications, the opposing ends of the side members 36 may extend beyond the inner surface 40 of the brace members 32 or beyond the brace members 32 themselves, so long as the frame 12 or other components of the Z-belt mechanism 10 do not obstruct the vertical movement of the carriage frame 34. 
     Extending between and mounted on the side members 36 are a pair of axles 42, each axle 42 being mounted for rotational movement about an axis of rotation relative to the side members 36. Each axle 42 is received through a pair of corresponding aligned apertures in the side members 36, although the axles 42 may alternately be mounted and carried either above or below the side members 36. 
     Removably connected to and mounted on each opposing end of each of the axles 42 are a pair of drive wheel assemblies 44 or a tensioning wheel assembly 46. 
     Referring to FIGS. 3, 10, and 11, it may be seen that each wheel assembly 44, 46 is constructed from a pair of thin, generally circular spaced-apart flange members 48 each having a larger diameter, with a generally circular center hub 50 of smaller diameter than the flange members 48 disposed between the flange members 48. The flange members 48 and center hub 50 are fastened together in any conventional manner such as by a plurality of threaded fasteners 52 which extend through apertures 54 in each o the flange members 48 and corresponding apertures 56 in the center hub 50, with a central opening 58 in each flange member 48 being aligned with and received on one of a pair of recessed grooves or extensions 60 on opposing sides of the center hub 48. The center hub 50 of each wheel assembly 44, 46 further defines a central bore 62 to slidably receive a portion of the axle 42 when the wheel assembly 44, 46 is mounted thereon, each wheel assembly 44, 46 being slidably received and keyed or locked to the corresponding axle 42 using conventional means such as a threaded fastener such that each wheel assembly 44, 46 rotates in unison with the corresponding axle 42 at the same angular rate of revolution. 
     Referring to FIG. 10, it may be seen that the outer cylindrical surface 64 of the center hub 50 of each tensioning wheel assembly 46 is generally smooth. Conversely, the outer surface 66 of the center hub 50 of each drive wheel assembly 44 defines a plurality of wide drive gear teeth 68. The center hub 50 of each tensioning wheel assembly 46 must have a width equal to the width of two drive wheel assemblies 44 plus the norma spacing between the two drive wheel assemblies 44 when mounted upon the axle 42 in order to permit proper alignment of the drive wheel assemblies 44 and opposing tensioning wheel assembly 46. While a pair of single tensioning wheel assemblies 46 have been shown herein with one tensioning wheel assembly 46 disposed on each one of the opposing sides of the carriage frame 34, it should be understood that a pair of tensioning wheel assemblies 46 sized similarly to the drive wheel assemblies 44 may be utilized on each side of the carriage frame 34 for a total of four tensioning wheel assemblies 46. 
     Referring again to FIGS. 1 and 3, it may be seen that two drive wheel assemblies 44 are disposed on each of the opposing ends of one axle 42, while a single tensioning wheel assembly 46 is disposed on each of the ends of the opposing axle 42. Each set of two drive wheel assemblies 44 is positioned on the exterior side of the adjacent side member 36 of the carriage frame 34, and each drive wheel assembly 44 is aligned with a portion of the corresponding tensioning wheel assembly 46 disposed on the opposing axle 42 and similarly positioned on the exterior side of the adjacent side member 36 of the carriage frame 34. 
     A plurality of flexible Z-tracks, Z-chains, or Z-belts 70 are looped over and carried on the drive wheel assemblies 44 and tensioning wheel assemblies 46 as shown in FIGS. 1-3. Referring to FIG. 7, each Z-belt 70 is comprised of a length of steel-belt material 72 having a planar side 74 with a textured rubber or other friction-producing coating, and a drive side 76 having a multiplicity of belt teeth 78 corresponding in size, depth, and spacing to the drive gear teeth 68 on the center hubs 50 of the drive wheels assemblies 44. The drive side 76 of the Z-belts 70 are similarly coated with a textured rubber or other friction-producing coating. 
     Each Z-belt 70 has an approximate length sufficient to extend linearly between the top end 80 and the bottom end 82 of the brace members 32, plus the distance between two opposing brace members 32 at the front and back of the frame 12. 
     Referring particularly to FIGS. 1 and 3, a first Z-belt 70 is connected to one of the rear brace members 32 near the bottom end thereof by a clamping assembly 84, the end of the first Z-belt 70 and corresponding brace member 32 being most closely adjacent t a first one of the set of two drive wheel assemblies 44. The first Z-belt 70 is oriented such that the planar side 74 is facing the brace member 32 and spaced a short distance therefrom, and the belt teeth 78 of the drive side 76 of the first Z-belt 70 are facing the drive gear teeth 68 of the corresponding drive wheel assembly 44. The first Z-belt 70 extends upwardly from the clamping assembly 84 at the bottom end 82 of the brace member 32 and over the outer rear and top sides of the center hub 50 of the adjacent drive wheel assembly 44 between the flanges 48 thereof, forwardly and downwardly to the opposing aligned tensioning wheel assembly 46 around the bottom and outer front sides of the center hub 50 of the tensioning wheel assembly 46, and upwardly to the top end 80 of the front brace member 32. The end of the first Z-belt 70 is connected to the front brace member 32 near the top end 80 thereof by a similar clamping assembly 84. 
     A second Z-belt 70 is connected to the top end 80 of the rear brace member 32 to which the first Z-belt 70 is connected. The second Z-belt 70 extends downwardly from the top end 80 of the rear brace member 32 and around the outer rear and bottom sides of the center hub 50 of the second drive wheel assembly 44 adjacent the first drive wheel assembly 44 on which the first Z-belt 70 is carried. The second Z-belt 70 similarly extends forwardly but upwardly to the opposing aligned tensioning wheel assembly 46, around the top and outer front sides of the center hub 50 of the tensioning wheel assembly 46, and downwardly to the bottom end 82 of the front brace member 32. The end of the second Z-belt 70 is connected to the front brace member 32 near the bottom end 80 thereof by a clamping assembly 84. 
     As shown in FIGS. 1 and 3, the second Z-belt 70 and associated drive wheel assembly 44 and tensioning wheel assembly 46 are situated generally within a plane disposed between the adjacent side member 36 and a similar plane defined by the first Z-belt 70 and associated drive wheel assembly 44 and tensioning wheel assembly 46. 
     Referring again to FIGS. 1 and 3, third and fourth Z-belts 70, as well as their associated drive wheel assemblies 44 and tensioning wheel assembly 46, are positioned on the opposing side of the carriage frame 34 from the first and second Z-belts 70. Each of the third Z-belt 70 and and fourth Z-belt 70 is similarly situated in a plane along with their associated drive wheel assembly 44 and tensioning wheel assembly 46, with the orientation of the third and fourth Z-belts 70 being symmetric to the orientation of the first and second Z-belts 70 across a plane of reflection parallel to length of extent of the side members 36. In some applications, it may be desired that this orientation be reversed from the first and second Z-belts 70, or that orientation and position of one or all of the four Z-belts 70 be modified so as to be non-symmetric. 
     Referring to FIGS. 1-3 and 5-9, it may be seen that the clamping assemblies 84 provide a means to securely and engagingly fasten or secure each of the opposing ends of the Z-belts 70 to the upper or lower ends 80, 82 of the brace members 32, and to selectively adjust the longitudinal tension on those Z-belts 70. 
     Referring particularly to FIGS. 5 and 6, one embodiment of the clamping assembly 84 is shown, that clamping assembly 84 being one of the four clamping assemblies 84 positioned on the lower ends of the vertical brace members 32 from which the Z-belts 70 extend upwardly. In this embodiment of the clamping assembly 84, the Z-belt 70 is disposed between an L-shaped backing plate 86 having a projecting leg 88 fixedly attached to the lower end thereof, and a movable clamping plate 90 disposed a distance in front of the backing plate 86. The backing plate 86 is connected to the end of the vertical brace members 32 by an extension bracket 92 which is bolted or otherwise fastened to the end cap 94 of the brace members 32 using a threaded fastener 96. The extension bracket 92 extends forwardly or rearwardly from the front or rear face brace member 32, and defines an aperture through which a threaded tensioning fastener 98 is received. The upper end of the threaded tensioning fastener 98 is received in a threaded aperture 100 and secured to the 88 projecting leg 88 of the backing plate 86, or may alternately be fixedly attached to the projecting leg 88. The opposing lower end of the threaded tensioning fastener 98 is received through a correspondingly threaded aperture in the extension bracket 92, and fastened at a particular position or elevation relative thereto using a pair of correspondingly threaded hex nuts 102 or similar fastening devices. Rotation of the hex nuts 102, or rotation of the threaded tensioning fastener 98 relative to the hex nuts 102, will cause the threaded tensioning fastener 98 to move in a linear direction generally normal or perpendicular to the extension bracket 92, thereby tightening or loosening the Z-belt 70 by increasing or decreasing the tension applied thereto. Referring to FIG. 6, it may be seen that the inner surface 104 of the clamping plate 90 defines a plurality of horizontal grooves or teeth 106 which are sized and shaped to mesh with the belt teeth 78 on the drive side 76 of the Z-belt 70, while the inner surface 108 of the backing plate 86 may be smooth or have a roughened or knurled texture to provide additional friction between the backing plate 86 and the Z-belt 70. The end of the Z-belt 70 is secured between the clamping plate 90 and the backing plate 86 by a plurality of threaded clamping plate fasteners 110 which extend entirely through apertures in the clamping plate 90 perpendicular thereto and are disposed on opposing sides of the Z-belt 70. The clamping plate fasteners 110 are received within aligned apertures 112 in the backing plate 86, rotation of the clamping plate fasteners 110 forcefully urging the clamping plate 90 toward the backing plate 86 and into engaging and clamping contact with the Z-belt 70. The enlarged heads 114 of the clamping plate fasteners 110 are preferably flush with the outer surface 116 of the clamping plate 90, and may be tightened or loosened using a hex-key, Allen wrench, or similar tool. Similar clamping assemblies 84 may be utilized at the top ends of each of the brace members 32 and Z-belts 70, with the components of the clamping assemblies 84 being inverted across the horizontal axis. 
     In normal operation, sufficient longitudinal tension will be applied to each of the Z-belts 70 by the clamping assemblies 84, drive wheel assemblies 44, and tensioning wheel assemblies 46, such that the Z-belts 70 hold and constrain the carriage frame 34 in a predetermined orientation relative to horizontal. In most circumstances, this predetermined orientation will be near or exactly horizontal &#34;level&#34; as determined with relation to some portion of the carriage frame 34, with the criss-cross configuration of the Z-belts being used to establish and maintain the &#34;level&#34; horizontal orientation. Once the carriage frame 34 has been set to near-level, the threaded tensioning fasteners 98 of adjoining and opposing clamping assemblies 84 may be tightened or loosened (i.e., tightening the top clamping assembly 84 of one Z-belt 70 while loosening the bottom clamping assembly 84 securing the opposing longitudinal end of the same Z-belt 70) in unison to adjust the level or orientation of the carriage frame 34. By preventing rotation of the axle 42 and drive wheel assemblies 44 while tightening and loosening the corresponding ends of the Z-belts 70, the either side, end, or corner of the carriage frame 34 may be raised or lowered relative to one another to adjust the tilt or orientation of the carriage frame 34. Once set, the carriage frame 34 will maintain that set orientation as the carriage frame 34 is carried along the vertical path. Consequently, while a level horizontal orientation will be preferred in most applications, the carriage frame 34 may be set at some preferred angle, such as with one end raised or lowered relative to the opposing end, while the carriage frame 34 traverses the path. 
     Referring to FIG. 6a, it may be seen that the the orientation of the drive side 76 and the planar side 74 of the Z-belt 70 relative to the brace member 32 may be reversed, so that the drive side 76 faces the adjacent brace member 32. In such a case, the backing plate 86 and clamping plate 90 may be rotated 180° or one half turn on the threaded tensioning fastener 98 so that the clamping plate 90 is disposed between the brace member 32 and the backing plate 86, with the clamping plate fasteners 110 extending entirely through the clamping plate 90 so that the heads 114 may be easily accessed without obstruction by the brace member 32. Alternately, as shown in FIG. 6a, the orientation of the backing plate 86 and clamping plate 90 may remain unchanged, but the inner surface of the backing plate 86 may define the plurality of teeth 106, and the inner surface of the clamping plate 90 may be generally planar or textured. 
     Referring to FIGS. 8 and 9, an additional alternative of the backing plate 86 and clamping plate 90 is shown, wherein one or both of the backing plate 86 and clamping plate 90 define a generally rectangular notch 118 of approximately the same width as the Z-belt 70, and communicating to form a recess having a depth approximately equal to the thickness of the Z-belt, whereby the backing plate 86 and clamping plate 90 may be forcibly urged near or into contact with one another by tightening the clamping plate fasteners 110. 
     The position of the first and second Z-belts 70 may be reversed or interchanged relative to one another, as well as the third and fourth Z-belts 70. 
     Referring particularly to FIGS. 3 and 4, it may be seen that the vertical alignment of the carriage frame 34 may be augmented by a pair of pin and channel guide assemblies 120 attached in opposition to one another on one side of the carriage frame 34. The pin and channel guide assemblies 120 include a pin 122 fixedly attached to and extending forwardly or rearwardly from the associated end of the side frame member 36 of the carriage frame 34, the distal end 124 of the pin 122 being received within a generally rectangular groove or notch 126 in a C- or U-shaped guide channel 128. Each of a pair of the guide channels 128 extend in generally vertical alignment along and connected to two of the vertical brace members 32, and are positioned and aligned to maintain a uniform vertical path for the carriage frame 34 and prevent rotation or twisting of the carriage frame 34 about a vertical or Z-axis. 
     Referring again to FIGS. 1 and 3, it may be seen that the Z-belt lifting and stabilizing mechanism 10 is equipped with a drive mechanism 130 comprising a high torque and high rpm DC drive motor 132 coupled by a differential 134 or other motor linkage to and carried on the rear axle 42 with the carriage frame 34. The housing of the drive motor 132 and differential 134 is fixedly connected or coupled to the carriage frame 34 to prevent the drive motor 132 and differential 134 from rotating with the axle 42. The axle 42 may include a pickoff 135 to measure complete or partial revolutions of the axle 42, motor shaft of the drive motor 132, or drive wheel assemblies 44, or a similar timing mechanism may be incorporated to measure appropriate revolutions of the drive motor 132 or differential 134, the pickoff 135 preferably being contained within or connected to the housing for the drive motor 132 and differential 134. 
     In operation, the number and rate or angular velocity of revolutions of the axle 42 or drive motor 132 may be conveyed or read into a memory register within a CPU or other processing unit, and the number and rate of those revolutions compared to a chart of experimental readings or a mathematical formula or equation which relates the number of revolutions to the exact vertical linear registration or displacement of the carriage frame 34 relative to either a fixed point or the endpoint of the last vertical movement of the carriage frame 34, to determine a resultant displacement relative to the frame 12 or the fill tube 16. As such, output from the CPU can be fed directly to the drive motor 132 causing the axle 42 to rotate a desired number of revolutions in a selected direction (clockwise or counter-clockwise) at a desired angular velocity (RPM) to produce vertical movement of the carriage frame 34 in a selected vertical direction (up or down) at a desired linear velocity. This linear velocity may be expressed in terms of positive or negative units of length per unit of time, and the corresponding angular velocity may be expressed as a positive or negative number of revolutions or partial revolutions per unit of time. The linear distance which the carriage frame 34 moves will thereby be directly proportional to the number of revolutions or rotations of the drive wheel assemblies 46 and the corresponding axle 42, while the rate of ascent or descent of the carriage frame 34 will be directly proportional to the angular velocity of the drive wheel assemblies 46 and the corresponding axle 42. In situations in which the rate of ascent or descent is varied over the selected time interval during which the axle 42 and drive wheel assemblies 44 are being rotated, and the carriage assembly 34 is thereby being raised or lowered, the total resultant linear displacement D of the carriage frame 34 will be directly proportional to the total number of revolutions N r  of the axle 42, drive wheel assemblies 46, or motor shaft and a constant k 1  relating the unit rotation of the axle 42 or drive wheel assemblies 44 to a predetermined unit linear displacement, and will further be directly proportional to the integral over the selected time interval between times t 1  and t 2  of the product of the angular velocity v a  of the axle 42, drive wheel assemblies 44, or motor shaft and the time increment dt over which that angular velocity was maintained times the constant k 2  relating the unit rotation of the axle 42, drive wheel assemblies 44, or motor shaft to a predetermined unit linear displacement, thus producing the relationships: ##EQU1## 
     The Z-belts 70 will generally be tensioned sufficiently that the Z-belts 70 cannot ride over the outer peripheral edges of the flanges 48 on either the drive wheel assemblies 44 or tensioning wheel assemblies 46, thereby preventing the Z-belts from becoming misaligned, however to prevent injury if a Z-belt 70 should become misaligned or break, a guard 136 may be placed on each side of the carriage frame 34 extending outwardly and downwardly to cover the outer edge of the outermost Z-belt 70. Further, in addition to the control provided by the CPU, a separate manual control 138 including a kill switch in addition to up/down or on/off/reverse switches should be incorporated into the apparatus. 
     Referring to FIGS. 12-15, it may be seen that several other operable configurations of the drive wheel assemblies 44 and tensioning wheel assemblies 46 may be utilized in the Z-belt lifting and stabilizing mechanism 10. FIG. 12 shows an alternate configuration in which two drive wheels 44 and two tensioning wheels 46 are disposed on one side of the carriage frame 34, with the drive wheels 44 on opposing ends of the carriage frame 34. In such an embodiment, the Z-belts 70 may extend either upwardly or downwardly from the respective drive wheel assemblies 44, so long as one Z-belt 70 extends upwardly and one downwardly. FIG. 13 shows an alternate configuration in which two drive wheels 44 and two tensioning wheels 46 are disposed on the same side and the same end of the carriage frame 34, with the drive wheels 44 carried on the same axle 42 and aligned with the tensioning wheels 46 which are similarly carried on a single axle 42. FIG. 14 shows an alternate configuration in which one drive wheel 44 and one tensioning wheel 46 are disposed on each side of the carriage frame 34, with the drive wheels 44 being located proximate to opposing ends of the carriage frame 34. FIG. 15 shows an alternate configuration similar to that of FIG. 14 in which one drive wheel 44 and one tensioning wheel 46 are disposed on each side of the carriage frame 34, with the drive wheels 44 being disposed proximate to the same end of the carriage frame 34. As in each of the above configurations, the Z-belts 70 may extend either upwardly or downwardly from the respective drive wheel assemblies 44, so long as one Z-belt 70 extends upwardly and one downwardly from the respective drive wheels 44. It may be readily appreciated that while these various configurations and embodiments will prove suitable for some applications, the preferred embodiment of the Z-belt lifting and stabilizing mechanism 10 will generally provide superior stability for maintaining the predetermined horizontal orientation at high rates of linear movement along the vertical path and also be capable of supporting greater loads during operation without tilting. 
     It should also be understood that in many applications, the Z-belts 70, drive wheel assemblies 44, tensioning wheel assemblies 46, drive motor 132, and differential 134 will be the only components of the apparatus 10 which are subject to wear and the effects of wear on the components other than the Z-belts 70 will not be appreciable. Because the longitudinal tension on the Z-belts 70 can be adjusted, wear on the Z-belts 70 can be compensated for in order to maximize the life span of the Z-belts 70. The Z-belts 70 may still be changed at prescribed intervals, if desired, and it is unnecessary to disassembly the apparatus 10 or remove the apparatus 10 from the filling machine in order to change Z-belts 70 since the carriage frame 34 will remain suspended while individual Z-belts 70 are removed and replaced. 
     While the preferred embodiment of the above Z-belt lifting and stabilizing mechanism 10 has been described in detail above with reference to the attached drawing figures, it is understood that various changes and adaptations may be made in the Z-belt lifting and stabilizing mechanism 10 without departing from the spirit and scope of the appended claims.