CA1138767A

CA1138767A - Package forming apparatus

Info

Publication number: CA1138767A
Application number: CA000360232A
Authority: CA
Inventors: Arthur W. Stanek
Original assignee: Nordson Corp
Current assignee: Nordson Corp
Priority date: 1979-09-17
Filing date: 1980-09-15
Publication date: 1983-01-04
Also published as: GB2059337A

Abstract

Abstract of the Disclosure A cut off and sealing mechanism for a tubular film wrapper containing spaced articles including rotary shaft-mounted crimpers with confronting film-engaging faces producing closing and sealing or crimping of the film in the seal area, one of the crimpers being spring-mounted relative to the frame of the machine; one crimper containing a stationary cutting blade at the film-engaging face of the crimper; and the other crimper having a yieldable anvil blade to bear against the edge of the knife blade and yield under the influence thereof to maintain a predetermined pressure relationship between the knife blade and the anvil blade for producing cutting of the film.

Description

~ .38767 This invention relates to packaging apparatus and more particularly to the cut off mechanism of a wrapper by which a film in substantially tubular ~orm embraces spaced articles or containers moving along a conveyor line wherein the tubular wrapper is severed and closed as by sealing between the spaced articles.

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Tubular film wrappers are most oftsn made of heat-sealable material such as polyethylene film, or a wide variety of other heat-sealable plastics; however, in certain situations, the material of the film may be sealable to itself without applica-tion of heat, and sealable mexely by application of pressure.
The film materials will vary over a wide range in thickness, dependlng upon the necessary strength of the material in the wrapper and the nature of the article or goods being packaged.
The sizes and nature of the articles being packaged also vary over an extremely wide range, and may in some instances be hard goods such as tools and machlne parts, and in other instances may be boxes which contain one or more individual articles; or in other instances the goods being wrapped may be fragile articles such as cookies or crackers which produce crumbs during handling.
Modern wrappers move the film and articles being wrapped along through the machlne at speeds which are typically in the range of 50 to 300 inches per minute, and 500 inches per minute is not particularly excessive speed. Depending upon the size of the packages being formed, the wrapper will make up to 250 ` ~.3~6~

packages per minute, each of which must be cleanly cut from the tube film between the spaced articles being wrapped. Of course, the ends of the packages being formed are also sealed closed at the same time the cuttlng is effected.
In the prlor art, the plastic wrapper has been cut in several ways. In one type of cutting arrangement, the tubular film wrapper with the articles enclosed therein passes between revolving shafts which carry crimper~ or sealers for sealing the ends of the packages as they are being cut. A knife which is confined in a slot in one of the crimpers is momentarily project-ed out of the slot to sllce through the film as the crlmpers engage and seal the fllm closed. The knife which moves radially with respect to the shaft moves into a slot in the other crimper as it completes the cutting operation, and then the knife is quickly withdrawn to be ready for the next cutting operation.
Although this type of reciprocating knife arrangement is widely used, it is complicated and expensive to build and maintain.
Another type of cutting arrangement in the prior art uses the similar revolving crimpers as described above. One of the crimpers carries a substantially flat and stationary anvil;
and the other of the crimpers carries a knife with a cutting edge to cooperate with the anvil face for cutting the film moving between the revolving shafts and crimpers. In this construction, the proper setting of the location of the knives with respect to the anvil faces and the proper location of the crimpers with respect to each other is extremely critical. The knife must be adjusted with respect to the anvil 50 that the edge of the knife barely kisses the surface of the anvil without applying any , --1~3~76~

excessive pressure. This setting causes the knife to cleanly sever the thicknesses of the film wrapper. However, the knife adjustment is very critical; and if the knife is backed away from the anvil as little as 0.001 inch, the cut off of the film wrap-per will not be reliably complete. A mere change in the heat conditions in the crimper which mounts the knife and anvil may ; change the optimum setting of the knife. Decreasing the heat in the crimper will cause the kni~e to back away from the anvil due to metal contraction, thereby preventing good and clean cut off.
An increase in the heat will cause interference between the knlfe and anvil, resultlng in abnormally high wear on the sharp knife edge.
In this prior art cut off arrangement wherein the knife is stationary with respect to the revolving shaft, and the anvil is also statlonary with respect to the adjacent revolving shaft, the wrapping machine may requlre a new knlfe or a reground knife approximately every month of operation in order to assuredly cleanly cut each package from the tube of film stock moving through the wrapping machine, Obviously, as the knives must be

2~ replaced and readjusted, the machine must be shut down with the associated loss of very valuable production time. In situations where short packages are being wrapped, two or four separate crimpers and cut off knives are carried on one of the shafts and corresponding two or four crimpers and anvils are carried on the other shaft.
One other problem that is encountered in this type of cut off mechanism is the presence of obstructions in the cut off or seal area. Such obstructions may be cookie crumbs or

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small particles of material, or may be a wrinkled ilm, so as to increase the spacing between the crimpers adjacent the knives.
If a crumb or particle is in the crimper area, the crimpers will be moved apart slightly during the crimping and cut off operation due to movement of one of the shafts against the springs pressing its bearings toward the optimum position. When the crimper and knife are moved away from the other crimper and anvil, obviously a complete cut off cannot be attained.

Summarv of the Invention An object of the invention is to provide a cut off and crimping mechanism for a tubular film wrapper which will reliably sever individual packages from the rapidly moving tube of film material which embraces the articles or goods being wrapped.
Another object of the invention is to provide a cut off and crlmping mechanism for a tubular film wrapper which will reliably sever the individual packages from the rapidly moving tube of fllm wrapping material and which will materially extend the life of the cutting blades which are used in severing the film.
A feature of the invention is to yieldably mount the anvil on springs in the revolving crimper which cooperates with the opposite revolving crimper which carries a stationary knife cooperating with the anvil in severing the film passing between the crimpers and associated knife and anvil.
Another feature of the inventlon is the yieldably mounting of one of the knife and anvil which are respectively disposed in opposite and cooperating revolvi g crimpers ~or closing the ends ,~, .
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of packages being severed from a high-speed moving tubular film, wherein one of the crimpers is yleldably mounted with respect to the other to accommodate limited variation in the thickness of the film and other obstructions therebetween during the sealing and cut off operation.
The particular advantage of the present invention is to reliably sever the tubular film wrapper at operating speeds necessary for modern commercial production and to avoid the interference of small particles or other obstructions that may exist in the seal area and also extend the life of the cutting blades used to produce the cutting of the film.

Brief DescriPtion of the Drawings Figure 1 is an elevation view of the crimping and cut off mechanism for the packaging machine.
Figure 2 is a side elevation view of the cut off and crimping mechanism.
Flgure 3 is an enlarged detail section view taken approximately at 3-3 in Figure 1 and illustrating the crimper and cut off mechanism at the moment of cutting the film passing therethrough.
Figure 4 is a detail section view, similar to Figure 3, and ~howing the crimper and cut off mechanism at a moment sub-sequent to complete cut off, Figure S is an enlarged detail view of one of the crimpers with the anvil mounted therein.

~13~q Detailed Specifi_ation One form of the invention is illustrated in the drawings and is described herein.
The wrapper cutting and closing mechanism is indicated in general by numeral 10, and includes upright frame members 11 which mount bearing blocks 12 and 13 respectively mounting rotatable shafts 14 and 15. The lower bearing blocks 12 are affixed to the frame as by cap screws 12.1 to predetermine the location of the shaft 14. The upper bearing blocks 13 are slidable along the inner edges 11.1 of the frame which define a guideway so that the shaft 15 may be moved slightly away from shaft 14 during opera-tion. Each of the movable bearing blocks 13 is urged downwardly by a spring 16, and an adjustable spacer may be provided for maintaining the minimum spacing between the shafts 14 and 15 and to resist the downward urging of the springs 16. A spring anchor mechanlsm 17 adjusts the downward thrust on the springs 16 so as ; to establish the resistance necessary to overcome in order to move the shaft 15 away from shaft 14.
The two shafts 14 and 15 have meshed gears 14.1 and 15.1 which coordinate the rotation of the two shafts. Input power is supplied to the shafts from a source of rotary power such as gear 18.
Crimpers 19 and 20 extend along and are affixed to the shafts 14 and 15, respectively, by cap screws 22. The crimpers 19 and 20 are provided with electric resistance heaters 23 to produce sealing heat at the film-engaging surfaces 19.1 and 20.1 thereof. In the form shown, the film-engaging surfaces 19.1 and 20.1 of the crimpers have serrations extending transversely , , .

113~767 across these film-engaging surfaces for producing similarly shaped crimped surfaces of the film material F at the seal areas F'.
The upper crimper 20 has an elongate slot 24 extending substantially throughout the entire length thereof. An elongate knife blade 25 is confined in the slot 24 and is confined in stationary relation in the slot 24 as by a plurality of set screws 26 located at spaced locations along the length of the blade. It will be recognized that the knife blade 25 has a cutting edge adjacent the adjoining film-engaging surface 20.1 of the crimper 20. The sharpened edge of the knife blade 25 protrudes slightly beyond the surface 20.1 for efficiently severing the film F in the crimp area. It has been found prefer-able to shape the sharpened edge of blade 25 to extend very sllghtly spirally or helically of the rotation axis of shaft 15, so as to effectively cause the cutting edge to engage and cut the plastic film progressively from one end of the blade 25 to the other end thereof as the shaft and blade revolve.
The other crlmper 19 also has an elongate slot 26 formed therein and extending along the length thereof. An elongate anvil blade 27 is confined in the slot 26, but is movable therein in a direction toward and away from the rotation axi~ of the shaft 14 and toward and ~away from the film-engaging face 19.1 of the crimper. The blade 27 has a plurality of apertures 28 therein to recelve hardened steel roll pins 29 which serve to retain the anvil blade in the slot 26. The roll pins 29 are confined in apertures 19.2 of the crimper.
It will be recognized that the aperture 28 in the anvil blade 27 is slightly larger than the diameter of pin 29 so that - the anvil blade 27 may move, to a limited extent, inwardly and outwardly of the slot 26.
The knife edge-engaging anvil surface 27.1 of the anvil blade is located approximately at the film-engaging surface 19.1 of the crimper so that the sharpened edge of the knife blade 25 may cooperate with the anvil face 27.1 in severing or cutting the film between the adjacent articles A confined by the tubular film.
A plurality of coil springs 30 bear against the rear edge of the anvil blade 27 and are confined in openings 31 in the crimper 19. Threaded plugs 32 are threaded into the threaded periphery of the openings 31 and serve as anchors for the springs 30. It will therefore be recognized that the anvil blades 27 may be retracted slightly into the crlmper 19 under influer.ce of pressure from the blade 25, as illustrated in Figure 3, and the spring 30 will maintain significant pressure against the anvil blade 27 so that the knife blade 25 and the anvil blade 27 will cooperate in cutting the plastic f ilm.
In operation, the spacing between the shafts 14 and 15 will initially be adjusted by the adjustable spacers 12.2 be-tween the bearing blocks 12 and 13 so that the springs 16 will normally urge the shaft 15 and the crimper 20 into the desired relationship with crimper 19. The two film-engaging faces 19.1 and 20.1 will allow space for the fi lm F therebetween, but will apply sufficient heat and pré~sure to the f ilm in order to produce a good seal in the seal area Fl.
In some instances where a suitable film is utilized, 113~76~7 heat may not be necessary in order to produce a seal, but pressure will be applied in order to adhere the film laminae together. The arcuately rounded shapes of the film-engaging surfaces 19.1 and 20.1 effectively cause these surfaces to roll along a short length of the film in the seal area F~ during the sealing and cutting process, substantially as illustrated in Figures 3 and 4.
As the film F and articles A are moving in the direction of arrow D, and the shafts 14 and 15 and the crimpers 19 and 20 are revolving in the direction of arrows b and c, respectively, the crimpers 19 and 20 will swing toward each other and squeeze the film into flattened condition in the seal area. The cutting edge of the knife blade 25 will bear against the film with significant pressure and will cut through the film as the edge of the knife blade bears against the anvil face 27.1 of the anvil blade. During the engagement of the sharpened edge of the knife blade 25 with the anvil face 27.1 of the anvil blade, the edge of the knife blade will cause the anvil blade 27 to recede slightly in groove 26, but the springs 30 will maintain the desired amount of pressure against the edge of the knife blade to assure complete cutting of the film.
; Subsequently, as the crimpers 19 and 20 roll past the dead center position, into the position illustrated in Figure 4, the film will have been severed as to produce a distinct and ~eparate complete package P sealed entirely shut. The arcuate ; faces 19.1 and 20.1 of the crimpers will gradually separate as the shafts revolve so as to allow the next article ~ to pass between the revolving shafts.
_ 9 _ 113fl767 Although the specificatlon illustrates only one crimper on each o the shafts 14 and lS, so as to accommodate articles of substantial length, it should be understood that, if it is desired to maintain approximately the same linear film speed in the direction of arrow D, and if articles of substantially shorter length are to be packaged, two or more crimpers on each of the shafts and coordinated with each other may be employed.
For instance, each of the shafts could have a pair of crimpers, - 10 disposed at 180 degrees with respect to each other; or it may be desirable to mount four crimpers on each shaft, each orient-ed at approximately 90 degrees with respect to each other. Of course, the suitable number of knife blades and anvil blades, spring-mounted, as illustrated herein, would be carried on the several crimpers.
It will be recognized that the permitting of the anvil blade 27 to move slightly in the slot 26 reduces the criticality of the adjustment as to locatlon of blade 25. The amount of pressure that is produced between the cuttlng edge of the knife blade and the anvil face 27.1 is controlled primarily by the strength of spring 30 and the adjustment thereof produced by the location of plug 32 in the opening 31.
Accordingly, it will be recognized that, simultaneously with the sealing of the film into closed condition at the end of ; the packages P being formed, the knife blade and anvil cooperate to apply the necessary cutting pressure so as to cleanly cut each package from the tubular film as the film and articles pass by the cutting mechanism 10.
An additional important function of.the yieldably '`` 113~76q mounted anvil blade 27 becomes apparent when consideration is given to the packaging of articles which may be brittle and produce crumbs or debrls inside the package. For instance, if some type of an abnormality were to occur or exist in the seal area F' of the film between the film-engaging faces 19.1 and 20.1 of the crimpers, it may be that the predetermined relation between the two faces 19.1 and 20.1 cannot be maintain-ed. Such an abnormality in the seal area may be a possible wrinkle in the film; or may be a piece of debris fractured from the article being packaged, such as a cookie crumb, if the articles being packaged are cookies. Other types of debris or small particles from the material being packaged could also find its way into the seal area of the film. When such an abnormality occurs, the crimpers 19 and 20 are rolled into con~ronting rela-tion with each other in the usual way, but, due to the presence of the abnormality or obstruction in the seal area, the upper crimper 20 is lifted slightly so as to be spaced somewhat further from the face of the lower crlmper 19. This occurs because the bearing block 13 for shaft 15 is permitted to move slightly against the pressure of spring 16. Although the prescribed amount of pressure to be exerted on the film may be reduced ; momentarily, an adequate seal may very likely occur. Further-more, because the anvil blade 27 is permitted to move, the spring 30 will cause the blade 27 to move outwardly of crimper l9 from the position illustrated in Figure 3 so as to maintain the pre-determined degree o~ pressure exerted against the cutting edge of the knife blade 25. As a result, even though the obstruction in the seal area caused the crimper 20 to lift slightly off the crimper l9, the efficient cutting action between the blade 25 " 1~3B~67 and the anvil blade 27 will occur and the cut will be cleanly made and without fail. Of course, when the seal area F~ contain-ing the obstruction moves away from the cut off mechanism 10, the springs 16 will move the bearing blocks 13 back into predetermin-ed position and the crimper 20 will be returned to its normal relation to the crimper 19 for adequately sealing and severing the next length of film after the shafts and crimpers have made one more revolution.
Whereas the yieldable blade in this disclosure comprises the anvil blade, it may be desirable under certain circumstances that the knlfe blade should be the yieldable part.
It will be seen that this invention provides a cut off mechanism for a tubular film wrapper wherein both the anvil blade is yieldable as it engages the edge of the knife blade, and acting in conjunction with thi~ yieldability ls the yieldability of the bearlng blocks 13 to permlt the crlmper 20 to move slight-ly away from the crimper 19 in order to accommodate slight abnormalities including obstructions in the seal area.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Apparatus for transversely cutting a rapidly moving tubular film wrapper between the spaced articles confined in the wrapper and closing the cut ends of the wrapper to form individual article-confining packages, comprising frame means, a pair of revolving parallel shafts on the frame means and spaced from each other to permit travel of the tubular film wrapper and articles therebetween, a pair of elongate crimpers each on a respective shaft and located to confront and cooperate with each other to engage and press the film wrapper together as the shafts and crimpers revolve, the crimpers having arcuate film-engaging surfaces confronting each other in closely spaced relation as the crimpers revolve, each of the crimpers having elongate slots extending longitudinally thereof and opening through the film-engaging surface thereof, an elongate knife blade in the slot of one of the crimpers and having a cutting edge disposed adjacent the film-engaging surface thereof, an elongate anvil blade in the elongate slot of the other of the crimpers and confronting the cutting edge of the knife blade as the crimpers revolve, the anvil having a knife-engaging anvil face disposed adjacent the film-engaging surface of the crimper, one of the elongate blades being movable inwardly and outwardly of the slot in the crimper and toward and away from the adjacent film-engaging surface of the crimper, and spring means bearing against said one movable blade and urging the blade outwardly of the slot and toward the film and permitting yielding of the blade inwardly of the cutting edge of the knife blade and the anvil face of the anvil blade.

2. The invention according to claim 1 wherein one of the shafts has spring-pressed bearing means permitting limited movement of the shaft toward and away from the other of the shafts when an abnormality of increased thickness in the film wrapper occurs between the cooperating crimpers.

3. The invention according to claim 1 wherein the anvil is movable inwardly and outwardly of the slot of the crimper and toward and away from the adjacent film-engaging surface, and spring means bearing against the anvil and urging the anvil outwardly of the slot and toward the film and permitting yielding of the anvil inwardly against the spring means and in response to pressure on the anvil face by the cutting knife.

4. The invention according to claim 3 and said spring means being confined in cavities adjacent the slot and within the crimper.

5. The invention according to claim 3 and pin means engaging and confining the anvil in the slot of the crimper.

6. The invention according to claim 4 wherein one of the shafts has spring-pressed bearing means permitting limited move-ment of the shaft toward and away from the other of the shafts when an abnormality of increased thickness in the film wrapper occurs between the cooperating crimpers,