US20130327805A1

US20130327805A1 - Material handling machine and method

Info

Publication number: US20130327805A1
Application number: US13/874,866
Authority: US
Inventors: Scott H. Baube; Thomas W. Vaitonis
Original assignee: Calvary Applied Tech LLC
Current assignee: Calvary Applied Tech LLC
Priority date: 2012-05-01
Filing date: 2013-05-01
Publication date: 2013-12-12

Abstract

The present invention is directed to a machine and method for moving and cutting a continuous web of material. In a preferred embodiment, the machine is a high speed snack bag handling machine operable to move and cut individual filled bags from a continuous web of filled and connected snack bags. Web movement through the machine is achieved by a hand-over-hand movement of a pair of bag grippers which each further include an extendable cutting blade to cut and separate individual bags from the web.

Description

This application claims priority to U.S. Provisional Application Ser. No. 61/641,011 filed May 1, 2012.

BACKGROUND OF THE INVENTION

The present invention relates to material handling. More particularly, the present invention relates to a machine and method for high speed moving and cutting of a continuous web of material. In a preferred embodiment, the present invention is directed to a high speed snack bag handling machine and method.
Material handling is involved in most aspects of present day industrial manufacturing and automation. Raw and processed materials used to manufacture a product require handling as they move through the production line. Automated machinery is commonly used to increase the manufacturing efficiency while reducing cost. Such automated machinery is many times custom built according to the type of material being handled.
One of the primary duties of material handling equipment is to move in-process manufacturing material from one production process to another on the manufacturing floor. Some material handling machinery performs a production step on the material and also transports the material to the next material process station using either integrated material moving components and/or auxiliary robotic machinery, for example.
In high speed manufacturing, material handling machine downtime is to be minimized and preferably avoided if at all possible. It is therefore very important that the high speed material handling machinery be made extremely robust so that it is able to withstand the constant vibrations and forces created by the moving machine components, yet also be able to quickly deal with (preferably with little or no downtime) slight variations in material sizes and feed rates which are common in such a high speed manufacturing environment. Present day technology may offer many machine solutions which would achieve the above objectives, however, very sophisticated machinery usually also means very high cost. There are many manufacturing processes where sophisticated high speed technology solutions are not feasible from a cost to manufacture standpoint. The challenge thus becomes one of designing a machine that achieves the above performance objectives while at the same time uses cost-effective components.

SUMMARY OF THE INVENTION

The present invention provides a material handling machine and method which achieves the above performance objectives and is a relatively low cost machine solution.
More particularly, the present invention provides a machine and method for the high speed handling of a continuous web of material. In a preferred embodiment, the present invention comprises a high speed snack bag handling machine and method which is operable to move an elongated web of joined and filled snack bags and perform a cutting operation which separates each bag from the web. Although the invention as herein described and shown in the drawing figures is directed at the specific embodiment of snack bag handling, it is understood that the teachings of the invention is not limited thereto and may be adapted to other material handling operations.
In the preferred embodiment, the material handling machine includes a pair of bag grippers which are operable to grip, move and cut a web of joined bags, previously filled with product at an upstream operation, into separated bags which are then prepared for sale (e.g., shipped to a warehouse or retail store). The bag grippers are mounted in laterally spaced relation to each other along a pair of parallel, spaced guide rails. The grippers are operable to move along their guide rails in a synchronized, “hand-over-hand” fashion where the grippers alternate between respective raised and lowered positions such that when one gripper is moving to its raised position, the other is moving to its lowered position.
The bag grippers each include bag gripper arms and respective jaws that may be moved between open and closed positions. As one gripper moves from the lowered position to the raised position along its guide rail, the gripper jaws thereof are in their open position and not engaging the web. The web is thus free to travel in between the open gripper jaws. When the gripper is open and being raised, the other gripper jaws are closed and being lowered (and carrying the captured web along with it). Since the first gripper is open as it is raised, the second gripper, along with the web it is holding, is lowered and passes between the spacing of the open gripper jaws as the grippers pass each other. This synchronized and constantly alternating movement of the grippers is what is referred to herein as gripper-over-gripper or “hand-over-hand” movement of feeding the web through the machine.
A cutting blade is mounted within one of the gripping jaws of each gripper. When a gripping arm is lowered with the web captured between its gripping jaws, the cutting blade is then extended which severs the web at the gripped location which is between two adjoining bags. The lower-most bag is thus cut free from the web and may be deposited into a shipping container or delivered to another location as required.

DESCRIPTION OF THE DRAWING FIGURES

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become apparent and be better understood by reference to the following description of the invention in conjunction with the accompanying drawing, wherein:

FIG. 1A is a perspective view of a material handling machine according to an embodiment of the invention;

FIG. 1B is an enlarged, fragmented, side elevational view of the web of material seen in FIG. 1A;

FIG. 2A is an enlarged, perspective view of a part of the machine of FIG. 1 showing the gripper arms in a first position;

FIG. 2B is an enlarged, perspective view of a part of the machine of FIG. 1 showing the gripper arms in a second position;

FIG. 3A is a perspective view of a gripper arm shown in the open position;

FIG. 3B is the view of FIG. 3A showing the gripper arm in the closed position;

FIG. 3C is an enlarged, fragmented view in cross-section of the gripper arm linkage mechanism;

FIG. 3D is a further enlarged, fragmented view in cross-section of the right linkage components seen in FIG. 3C;

FIG. 4 is an enlarged, perspective view of the gripper arm seen in FIG. 3A and further including a cam block and cam rollers;

FIG. 5 is an enlarged, perspective view in cross-section of the gripper jaws in the closed condition with the web captured therebetween and ready for cutting;

FIG. 6A is a front elevational schematic of an alternate crank arm drive mechanism of the invention;

FIGS. 6B, 6C and 6D are side elevational schematics of an alternate crank arm drive mechanism of the invention; and

FIGS. 7A and 7B are enlarged detail views of portions of FIGS. 6C and 6D, respectively.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to the drawing figures, there is seen in FIG. 1A an embodiment of the invention comprising a snack bag handling machine 10 designed for high speed separation of individual snack bags 12 a from a continuous snack bag web 12. While the embodiment shown and described herein is used for separation of individual snack bags form a continuous web of snack bags, it will be appreciated that the invention may be adapted to many other material handing operations and is not limited to snack bag handling. Furthermore, illustrations and references to relative movement direction and orientation of components discussed herein shall not be construed in a limiting sense, it being understood that the invention may be used in a variety of orientations as required.
As seen in FIG. 1A, a continuous snack bag web 12 is directed to machine 10 from an upstream bag filling operation 14 where a consumable (e.g., chips) is deposited and sealed into individual, linearly spaced bags 12 a along web 12. As seen best in FIG. 1B, each bag 12 a is defined between a pair of laterally extending seals 12 b (e.g., by heat sealing facing panels of material 12 c and 12 d together).
Machine 10 includes a pair of bag grippers 16 and 18 operable to grip, move and cut web 12 into separated bags 12 a which are then prepared for sale (e.g., shipped to a warehouse or retail store). For example, once cut free of continuous web 12 by one of the grippers 16, 18, the individual snack bag 12 a may be deposited into a shipping box 20. It is understood that the Figures herein show but one possible embodiment of a snack bag boxing operation and the invention is not to be limited thereby. In this embodiment, a plurality of empty boxes 20 are fed from a supply ramp 22 to a location beneath bag grippers 16, 18 such that the cut bags 12 a may be directed into a box 20. The bags 12 a may be deposited in any desired array within box 20. The array pattern may be controlled by moving box 20 and/or the individual bags 12 a (after each bag 12 a is cut free of the web) into the desired box (or other container) location. Any desired positioning control mechanism may be used including vacuum chucking, pulsed air streams and/or robotic arms, for example. Such control mechanisms may be programmable such that they may be adjusted to change array patterns and bag sizes as required for a particular job.
As seen in FIGS. 2A and 2B, bag grippers 16, 18 are mounted in laterally spaced relation to each other along guide rails 62, 64, respectively. Although not strictly necessary, it is preferred that grippers 16, 18 are substantially identical and description of one gripper and associated components herein is understood to apply equally to the other gripper and associated components. As will be described in detail below, grippers 16, 18 are operable to move along guide rails 62, 64 in a synchronized, “hand-over-hand” fashion. FIG. 2A shows a position where gripper 16 is at its raised position and gripper 18 is at its lowered position. In FIG. 2B, gripper 16 is shown in its lowered position and gripper 18 is shown in its raised position. During operation, grippers 16 and 18 alternate between their respective raised and lowered positions such that when one gripper is moving to its raised position, the other is moving to its lowered position. This movement then reverses with grippers 16 and 18 continuously gripping and feeding web 12 through machine 10 as described in more detail below.
FIGS. 3A-3D illustrate various views of gripper 16, it being understood gripper 18 is preferably substantially identical thereto as mentioned above. As seen in FIGS. 3A and 3B, gripper 16 includes first and second gripper arms 16 a, 16 b individually pivotally mounted at pivot points P₁and P₂, respectively, to a bracket 30. Movement about pivot points P₁and P₂allow gripper arms 16 a and 16 b to alternately move toward and away from each other. Each gripper arm 16 a, 16 b is inwardly angled at pivot points P₁and P2 and define upper arm segments 16 a′ and 16 b′ and lower arm segments 16 a″ and 16 b″, respectively. Lower arms segments 16 a″ and 16 b″ each include a respective gripper jaw 16 a′″ and 16 b′″ which extend substantially perpendicular to their respective gripper arms 16 a, 16 b. Gripper jaws 16 a′″ and 16 b′″ each include a respective jaw surface 19 and 21 (see also FIG. 5) to be discussed in more detail below.
As stated above, gripper arms 16 a and 16 b move alternately toward and away from each other about pivot points P₁and P₂. FIG. 3A illustrates gripper arms 16 a, 16 b in their open (away from each other) position and FIG. 3B show gripper arms 16 a, 16 b in their closed (toward each other) position. When moved toward one another to the closed position seen in FIG. 3B, the facing web jaw surfaces 19 and 21 physically capture web 12 therebetween, preferably at the location of a bag closure seam 12 b. When moved away from each other to the open position seen in FIG. 3A, the facing web jaw surfaces 19 and 21 separate and release web 12 which then may move separately of gripper 16.
As seen in FIG. 3C, relative movement between gripper arms 16 a and 16 b is assisted via a linkage mechanism 32 which interconnects gripper arms 16 a and 16 b at upper arm segments 16 a′ and 16 b′. Mechanism 32 includes first and second linkages 34 and 36 pivotally connected to each other at pivot point P₃. First and second linkages 34 and 36 are preferably substantially identical to each other and description of one herein is understood to apply to the other. First and second linkages 34 and 36 each include respective first and second linkage components 34 a, 34 b and 36 a, 36 b. The second linkage components 34 b and 36 b of each linkage are each pivotally connected to upper arm segment 16 a′ and 16 b′ via pivot points P₄and P₅, respectively. First linkage components 34 a and 36 a are pivotally connected to each other at pivot point P₃. Pivot points P₁, P₂, P₃, P₄and P₅all extend in spaced, parallel relation to one another.
As seen best in FIG. 3D, first and second linkage components 36 a and 36 b may translate relative to one another and are biased toward one another via a spring 40. More particularly, in one possible embodiment, second linkage component 36 b includes a hollow projection 36 c which telescopes between spaced fingers 36 a′ and 36 a″. Spring 40 is located within the hollow passage 36 c″ of projection 36 c and includes a first end 40 a which is located at end wall 36 c′ of projection 36 c. A bolt 42 (e.g., a shoulder bolt) passes freely through a washer 43 located at spring end 40 b with bolt head 42 b abutting washer 43. The shank of bolt 42 passes through spring 40 and exits component 36 b through aperture 36 c′″ formed in end wall 36 c′. Bolt 42 includes a threaded end 42 a which threads into hole 36 a′″ of linkage component 36 a thereby anchoring bolt end 42 a to component 36 a. FIG. 3D shows linkage components 36 a and 36 b slightly spaced from one another which forms gaps such as indicated at G1, G2 and G3 between the first and second linkage components 36 a and 36 b. Alignment dowels 44 and 46 may be inserted between respective aligned holes formed in linkage components 36 a and 36 b. Either one of the linkage components 36 a, 36 b is not fixed to the dowels such that that component may slide freely on the dowels relative to the other component.
As seen in FIG. 3A, when first and second linkages 34 and 36 are in an angled position relative to one another, first and second gripper arms 16 a, 16 b are in their open position, i.e., gripper arm upper segments 16 a′ and 16 b′ are moved toward each other and lower arm segments 16 a″ and 16 b″ and thus also gripper jaws 16 a′″ and 16 b′″ are moved away from each other.
As seen in FIG. 3B, when first and second linkages 34 and 36 are in substantially coplanar relationship to one another, first and second gripper arms 16 a, 16 b are in their closed position, i.e., gripper arm upper segments 16 a′ and 16 b′ are moved away from each other and lower arm segments 16 a″ and 16 b″ and thus also gripper jaws 16 a′″ and 16 b′″ are drawn toward one another.
Various mechanisms may be employed to control linkage movement between the coplanar and angled positions described above. In the embodiment shown in the Figures, the linkage control mechanism includes a trigger rod 50 which connects to and extends between linkages 34 and 36 at the location of and substantially perpendicular to pivot point P₃. Rod 50 includes a head 50 a having a central bore 52 extending therethrough (FIG. 3C). To assist in maintaining proper alignment, the shaft of rod 50 may freely extend through a guide block 32 fixed to bracket 30. As seen best in FIG. 2B, a cylinder and piston type assembly 54 and 56 is associated with each gripper arm 16 and 18 and may be mounted to a bracket upper wall 30 a which is spaced above linkages 36 and 34, respectively. Piston rods 54 a and 56 a extend coaxially with respect to the trigger rod 50 of the respective linkage 36 and 34 and may move between raised and lowered positions. When in the raised position, piston rods 54 a and 56 a are linearly spaced from their respective trigger rod 50. When in the lowered position, piston rod lower end 54 b, 56 b extends into a respective trigger rod end 52 with a further downward force causing linkages 34 and 36 to pivot about pivot point P₃and move to their coplanar position seen in FIG. 3B.
As seen best in FIG. 2B, piston stops 58 and 60 are mounted on respective guide rails 62 and 64. When gripper arms 16 and 18 are alternately raised along spaced guide rails 62 and 64, respectively, upper piston end 54 a and 56 a will abut piston stops 58, 60, respectively, with further upward movement of the gripper arms 16, 18 causing the piston stops to exert a downward force against the piston rods which moves them to their lowered positions. As discussed above, when piston rods 54, 56 are lowered, lower piston rod end 54 b, 56 b abuts a respective trigger rod 50 and pushes it downward causing linkages 36 and 34 to pivot about pivot point P₃and move into their coplanar relationship. It is noted in FIG. 2B that a vertically adjustable rod 58′ may be provided to act as the piston stop allowing the operator to adjust the vertical positioning thereof to adapt to the needs of a particular job (e.g., when the size and thus spacing between the individual bags 12 a changes the piston stop potion may likewise be changed to ensure the web is gripped at the appropriate location).
Various drive mechanisms may be used to alternately raise and lower gripper arms 16, 18 along rails 62, 64. For example, linear actuators within guide rails 62 and 64 may be used. Alternatively, a crank arm drive mechanism such as seen in FIGS. 6A-6D may be used. The crank arm drive mechanism may afford a higher degree of robustness as compared to linear actuators as will be discussed more fully later.
As gripper arm 16 moves from the lowered position to the raised position along guide rail 62, gripper jaws 16 a′″ and 16 b′″ are in their open position (FIG. 3A) and not engaging web 12. Web 12 is thus free to travel between gripper jaws 16 a′″ and 16 b′″. Furthermore, as previously mentioned, when gripper 16 is open and being raised, gripper 18 is closed and being lowered (and carrying web along with it). Since gripper 16 is open as it is raised, gripper 18, along with web 12, passes between the spacing of open gripper jaws 16 a′″ and 16 b′″ as the grippers 16 and 18 pass each other. This synchronized and constantly alternating movement of the grippers 16 and 18 is what is referred to herein as gripper-over-gripper or “hand-over-hand” movement.
As gripper arm 16 is raised, and upon piston rod end 54 a abutting and pressing further against piston stop 58, piston rod end 54 a is pushed downwardly against respective trigger rod 50 which is thus also forced downwardly causing associated linkages 34 and 36 to pivot about pivot point P₃to their coplanar relationship. As linkage components 34, 36 are moved to their coplanar relationship, they apply an outward force against their respective gripper upper arm segments 16 a′, 16 b′, thereby causing counter-clockwise (CCW) pivoting of gripper arm 16 a about pivot point P₁and clockwise (CW) pivoting of gripper arm 16 b about pivot point P₂(FIG. 3C). This movement causes gripper jaws 16 a′″ and 16 b′″ to move toward one another to the closed position (FIG. 3B). Thus, when moved to the fully raised position, gripper arm lower segments 16 a″ and 16 b″ move toward one another causing gripper jaws 16 a′″ and 16 b′″ to also move toward one another and capture web 12 therebetween, preferably at seal seam 12 b as discussed above. Once web 12 has been captured between jaws 16 a′″ and 16 b′″, the drive mechanism lowers gripper 16 which takes the captured web 12 along with it. As discussed above, when gripper 16 is being lowered along with captured web 12, opposite gripper arm 18 is being raised in the open jaw position with gripper 16 passing between the open jaws of arm 18.
With trigger head 50 a seated against block 32, it will be appreciated that linkage components 34, 36 will stay in their coplanar relationship until a counter-force is applied at pivot point P₃. Gripper jaws 16 a′″ and 16 b′″ thus stay in the closed position during the lowering of gripper 16 along guide rail 62.
As seen in FIG. 2B, brackets 70 a and 70 b having a respective cam block 80 a and 80 b are attached to respective guide rail 62 and 64. Cam blocks 80 a and 80 b are laterally spaced from each other a distance slightly larger than the length “L” of gripper jaws 16 a′″, 16 b′″ and are positioned in the path of gripper arms 16, 18. As seen best in FIG. 4, cam block 80 a includes a pair of spaced flanges 81 and 82 which taper (widen) gradually toward one another in the downward direction. As such, the width of the spacing between the flanges narrows in the downward direction with the upper spacing width W₁being slightly larger than the lower spacing width W₂. Gripper jaws 16 a′″ and 16 b′″ are still in their closed position and gripping web 12 as they approach cam blocks 80 a and 80 b. Gripper jaws 16 a′″ and 16 b′″ further each include cam rollers 84 a, 84 b and 86 a, 86 b, and the lateral spacing of the cam blocks 80 a and 80 b are such that outer cam rollers 84 a and 86 a are directed through cam block 80 b and between cam flanges 81 and 82 thereof while at the same time inner cam rollers 84 b, 86 b are directed through cam block 80 a and between flanges 81 and 82 thereof. Since the spacing between the cam flanges 81 and 82 narrows in the downward direction, the cam rollers are forced even closer together as they travel therethrough.
Referring to FIG. 5, the gripper jaws 16 a′″ and 16 b′″ are seen in the closed position with web seam 12 b captured therebetween and prior to the cam rollers entering the narrowed width W₂of cam flanges 81 and 82. Web engaging bars 19 and 21 are each spring mounted to respective jaws 16 a′″ and 16 b′″. Bars 19 and 21 are biased by springs 90, 92 toward each other and in a direction away from their respective jaws 16 a′″ and 16 b′″. As discussed more fully below, a cutting blade 88 is provided having a cutting end 88 a extending through either one of the web engaging bars such as bar 21 with opposite, non-cutting end 88 b fixed to jaw 16 b′″ via bolt 89.
In the closed position seen in FIG. 5, jaws 16 a′″ and 16 b′″ are spaced a distance such that the outwardly biased web engaging bars are gripping web 12 therebetween. In this condition, a space S₁is defined between jaw 16 a′″ and bar 19 and a space S₂is defined between jaw 16 b′″ and bar 21. As the cam rollers travel through the narrowed width W₂between the cam flanges of their respective cam blocks, the cam rollers are squeezed even closer together. Since the cam rollers are mounted to jaws 16 a′″ and 16 b′″, and since bars 19 and 21 are already closed upon web 12, this further inward force causes the jaws 16 a′″ and 16 b′″ to move closer toward one another, pushing against the bias of springs 90 and 92, and thereby closing the spaces S₁and S₂. Since blade 88 is fixed to and moves with jaw 16 b′″, as space S₂closes, cutting end 88 a projects outwardly of web engaging surface 21 and passes through web seal 12 b, thereby cutting and separating the adjoining bags 12 a from each other. Once the cam rollers exit the cam block, the rollers are no longer held together by the cam block and the springs 90 and 92 bias bars 19 and 21 away from their respective jaws 16 a′″ and 16 b′″ causing blade cutting end 88 a to retract within bar 21.
Referring to FIG. 4, trigger rod 50 includes a lower end 50 b. Since trigger rod 50 is attached to linkage components 34 and 36, rod 50 lowers together with the lowering of the gripper arm 16 along guide rail 62. As the cam rollers exit the cam blocks, trigger rod lower end 50 b engages a stop surface 70 a of bracket 70. Further lowering of gripper arm 16 by the drive mechanism causes trigger rod 50 to be pushed upwardly with respect to gripper arm 16. Since trigger rod 50 is fixedly attached to linkage components 34, 36 at pivot point P₃, upward movement of rod 50 forces linkage components 34, 36 from their coplanar relationship into their angled relationship. This causes CW movement of gripper arm 16 a about pivot point P₁and CCW movement of gripper arm 16 b about pivot point P₂and thus movement of jaws 16 a′″ and 16 b′ away from each other and toward the open position which releases web 12. Since the cutting action has already occurred as described above, the lower-most bag 12 a is released from the web 12 for further downstream handling, e.g., deposit into a shipping container such as box 20.
It is noted that during the squeezing together of the cam rollers as they travel through the narrowed area of the cam blocks, further CW movement of upper arm segment 16 b′ occurs. Since linkages 32 and 34 are interconnected and already in their coplanar relationship, the outer linkage component 36 b is pulled away from linkage component 36 a against the bias of spring 40 and translates away from linkage component 36 a (FIG. 3D). Thus, once the cam rollers have exited and are no longer constrained together by the cam blocks, spring 40 urges linkage components 36 a and 36 b back toward each other and thereby closes the gaps G₁-G₃therebetween. This action assists in the movement of the jaws 16 a′″ and 16 b′″ away from each other toward the open position.
FIGS. 6A-6D illustrate another preferred embodiment of the invention having a crank arm drive mechanism and web position sensors. Components in FIGS. 6A-6D which are substantially the same as their respective components in FIGS. 1-5 are indicated by the same reference number increased by 100.
As in the embodiment of FIGS. 1-5, grippers 116, 118 are mounted to and operable to move along guide rails 162, 164 in a synchronized, “hand-over-hand” fashion. FIG. 6A shows gripper 116 in the fully raised position while gripper 118 is in the fully lowered position. Gripper 116 is mounted to ride along guide rail 162 and is moved by crank arm drive mechanism indicated generally at reference numeral 200. As in the embodiment of FIGS. 1-5, description of the components of crank arm mechanism 200 associated with gripper 116 applies to the same respective components of crank arm mechanism 211 associated with gripper 118.
Crank arm drive mechanism 200 includes a crank rod 210 having a first end 210 a pivotally connected to a crank arm 212 at pivot point P₆which passes through a selected one of a plurality of linearly spaced through holes H formed in crank arm 212 (FIG. 6B). As one moves the crank arm connection point from the end 212 b attached to the sprocket gear 214 and toward the distal (free) end 212 a of the crank arm 212, the diameter of the crank arm circle C, and thus also the distance of travel of the respective gripper mechanism 116 increases. Thus, when there is a product changeover and the length L₃of the web separable product 12 a increases, the travel distance necessary to grip the web in the appropriate location may likewise be increased by moving connection of the crank arm end 210 a (and thus also pivot point P₆) to one of the through holes located closer to crank arm distal end 212 a.
As stated above, crank arm 212 includes an end 212 a which is mounted to and driven by rotating sprocket gear 214 which itself is driven by drive sprocket gear 216 which is in turn driven by a motor (not shown). A looped belt B₁interconnects sprocket gears 214 and 216. The drive sprocket associated with each gripper assembly may be operated along a common drive shaft (not shown).
Crank rod 210 includes a second end 210 b which is pivotally attached to gripper mechanism 116 via a stop plate 220 which mounts to gripper mechanism 116 through a pivot connection 224 (FIG. 6A). Stop plate 220 is mounted to gripper mechanism 116 laterally of grip jaws 116 a′″ and 116 b″ at bracket 30, for example. Stop plate 220 is spring loaded and biased by spring 230 toward crank rod 210. As seen best in FIGS. 7A and 7B, a bolt 222 includes a threaded end 222 a which threads into crank rod end 210 b and is thus fixed thereto. Bolt 222 includes a smooth surfaced shank 222 b which extends from threaded end 222 a through a hole in stop plate 220. Bolt head 222 c is located on the side of stop plate 220 opposite crank rod 210. Spring 230 is mounted to bolt 222 and extends between stop plate 220 and bolt head 222 c. Spring 230 is mounted in a partially compressed condition which applies a biasing force F₁against stop plate 220 in a direction away from bolt head 222 c. This biases stop plate 220 against crank arm end 210 b and when in this position, crank rod 210 will travel a first linear stroke distance D₁which is equal to the diameter of crank circle C when traveling from the upper extent (twelve o'clock position) to the lower extent (6 o'clock position) (FIGS. 6B-6D).
Application of an opposing force F₂against stop plate 210 which is greater than the biasing force of the spring 230 pushes stop plate 220 away from crank rod end 210 b and further compresses spring 230 between stop plate 220 and bolt head 222 c. This position is seen in FIG. 7B wherein crank rod 210 has been linearly separated from stop plate 220 by a distance D₂. This effectively shortens the stroke crank rod 210 by a distance D₂(see FIGS. 6B and 7B) and thus also shortens the stroke length of gripper mechanism 116 (the total distance of stoke D_T=D₁−D₂) as described more fully below.
An eccentric stop 240 is mounted to sprocket 260 which is rotated by sprocket gear 262 via a motor (not shown) and looped belt B₂(FIG. 6B). The sprocket gears associated with an associated gripper arm may be driven along a common drive shaft. Eccentric stop 240 is rotated on command via signals received from a sensor 280 (FIG. 6A) positioned to detect the position of an approaching bag seam 112 b (or other appropriate detectable element on web 112) relative to the location of the grip location (where the gripper jaws of the upper-most gripper mechanism are about to be triggered closed on the web in the manner described above). If the position of the seam has varied from the location where the gripper jaws will be triggered to close, the sensor sends a command to the eccentric stop to make it rotate to a rotational position which will change the stroke length by an amount compensating for the variance.
More particularly, as seen in FIG. 6A, eccentric stop 240 is positioned at a location slightly above the location of gripper jaws 116 a′″ and 116 b′″when at the upper extent of travel. When the smallest radius of eccentric stop 240 is at the 6 o'clock position, stop plate 220 will abut eccentric stop 240 without application of force F₂which means plate 220 is biased against crank rod end 210 b and the travel distance of gripper 116 will thus be D₁. Should upstream sensor 280 detect that the position of a bag seam 112 b has varied from where it should be (i.e., at a location which, when speed of web travel is factored in, the sensor calculates it will arrive at the location of the gripper jaws at the exact moment they are triggered closed in the manner described above), a signal is sent from sensor 280 to rotate eccentric stop 240 such that it presents the appropriate radius thereof at the 6 o'clock position. For example, a larger eccentric radius at the 6 o'clock position means the stop plate 220 will abut the eccentric stop prior to crank rod 210 reaching its upper extent of travel such that its stroke (and gripper 116 to which it is attached) is adjusted. This adjusted distance of stroke travel may be of an amount anywhere between the smallest radius R_Sand largest radius R_Lof eccentric stop 240 (where R_L−R_S=D₂where D₂is the maximum amount of distance the crank arm stroke may be shortened. Once the stroke has been shortened, it may of course be again lengthened on command of sensor 280 by rotating the eccentric toward R_S. Depending on whether the variance is a foreshortening or a lengthening, the sensor will trigger the eccentric to rotate in the appropriate direction to present either a larger radius or smaller radius to the rising stop plate in order to compensate for the variance. In a preferred embodiment, the signal causing the eccentric stop to rotate to compensate for a variance may be at any desired point between the 6 o'clock and 12 o'clock positions of the crank arm revolution.
It is noted that the crank arms controlling the respective gripper arms 116 and 118 are 180° out of phase. As such, the weight of one gripper assembly is counter-balance by the weight of the other gripper assembly. This balances the machine which decreases the amount of energy required to drive the machine. Further, it will be appreciated that two product bags 12 a are processed (cut and transferred to processing location such as box 20) per input revolution.
It will thus be realized that sensor 280 and eccentric stop 240 may be used to ensure the desired web grip location (e.g., at a seam 112 b) is located at the gripper jaws when they are triggered closed. As such, slight variances, which inevitably creep into and cause the desired web grip location to be offset from the gripper jaws when triggered closed, may be compensated for without machine downtime or human intervention.
While this method and apparatus has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as described.

Claims

What is claimed is:

1. A high speed material handling machine comprising:

a) first and second parallel, spaced guide rails;

b) first and second gripper assemblies mounted to a respective guide rail in laterally spaced relation with one another, each gripper assembly including:

i) first and second gripper arms pivotally mounted to a bracket between an open and a closed position, each gripper arm including an upper arm segment and lower arm segment with the lower arm segment having a gripper jaw which extends substantially perpendicular to its respective gripper arm and includes a gripper jaw surface adapted to capture material therebetween when in the closed position;

ii) a linkage mechanism interconnected to the upper arm segments through first and second linkages which are pivotally connected to each other wherein each linkage includes respective first and second linkage components adapted to translate relative to one another and are biased toward one another by a biasing member; wherein the first and second linkages are in an angled position when the gripper arms are in the open position and are substantially coplanar to one another when the gripper arms are in the closed position;

iii) a linkage control mechanism to control movement of the linkage mechanism between the angled and substantially coplanar positions, the linkage control mechanism including:

a) a trigger rod connected to and extending between the linkages, the trigger rod having a head with a central bore;

b) a cylinder and piston assembly including a piston rod extending coaxially with the trigger rod wherein the piston rod is linearly spaced from the trigger rod when in an extended position and wherein the piston rod impacts the central bore of the trigger rod when in the compressed position thereby engaging the trigger rod to cause the linkages to pivot to the coplanar position; and

c) a drive mechanism to alternately raise and lower the gripper arm assemblies in a synchronized fashion wherein the first and second gripper assemblies alternate between a respective raised and lowered position,

wherein as one of the gripper assemblies moves from the lowered position to the raised position along its respective guide rail, the gripper jaws thereof are in the open position and not engaging the material such that the material is free to travel in between the open gripper jaws, and wherein when the one of the gripper assemblies is open and being raised, the gripper jaws of the other of the gripper assemblies are closed and being lowered thereby carrying the captured material such that it passes between the spacing of the open gripper jaws as the gripper assemblies pass each other.

2. The high speed material handling machine of claim 1 wherein at least one gripper assembly has gripper jaws equipped with a cutter.

3. The high speed material handling machine of claim 2 wherein the gripper assembly bracket of the gripper assembly carrying the gripper jaws equipped with the cutter includes a cam block having a pair of spaced flanges which taper gradually toward one another such that cam rollers situated on the gripper jaws engage the cam block between the spaced flanges thereby causing the gripper jaws to be increasingly directed toward one another such that the material captured between the gripper jaws is cut with the cutter.

4. The high speed material handling machine of claim 1 further comprising a piston stop mounted onto each respective rail wherein each respective piston rod impacts upon its respective piston stop thereby causing the piston rod to engage the trigger rod to pivot the linkages to the coplanar position.

5. The high speed material handling machine of claim 4 wherein the piston stop is adjustable.

6. The high speed material handling machine of claim 1 wherein the drive mechanism is a linear actuator.

7. The high speed material handling machine of claim 1 wherein the drive mechanism is a cam arm drive mechanism, the cam arm drive mechanism comprising a crank rod having a first end and a second end, wherein the first end is pivotally connected to a crank arm at a pivot point which passes through a selected one of a plurality of linearly spaced through holes formed in the crank arm and wherein the second end is pivotally mounted to a respective gripper assembly via a stop plate; and wherein the crank arm has a first end and a second end wherein the first end is attached to a rotating sprocket gear such that the pivot point is located between the rotating sprocket gear and the second end of the crank arm, and wherein the rotating sprocket gear is driven by a drive sprocket gear through a connecting looped belt.

8. The high speed material handling machine of claim 7 wherein the cam arm drive mechanism further comprises an eccentric stop adapted to receive command signals from a sensor so as to rotate the eccentric stop thereby adjusting a stroke length of said cam arm drive mechanism.

9. The high speed material handling machine of claim 7 wherein the crank arms are 180° out of phase.