US2923115A - Sealing mechanism for packaging machines - Google Patents

Description

Feb. 2, 1960 C. A. FRANK ETAL SEALING MECHANISM FOR PACKAGING MACHINES Filed April 23, 1957 3 Sheets-Sheet 1 r\ l N I -q n 1 l \9b E APPLICATOR I MOISTENED APPUCATOR MOVES mro AREA molsrausruaz SHlELDZ D I W'E FIG. FIG.2 FIG. 3

INVENTORS Joseph A. Lynch Carl A. Frank ATTORNEY HANISM FOR PACKAGING MACHINES 3 Sheets-Sheet 2 Filed April 23, 1957 FIG.5

INVENTORS Joseph A. Lynch A. Frank ATTORNEY Carl I I I llllllehnnflu VQ W m.ufl1

2 vi!!! rlllll'lli'lilllllfilllII (II 14, I v I I n v I I I I I I 1 k :5 Sheets-Sheet 3 Feb. 2, 1960 c, FRANK ETAL SEALING MECHANISM FOR PACKAGING MACHINES Filed April 23, 1957 w zum wwmiu 0 m w Mu m m 04m CIA-2m A m ell FL :5 H.535 W 3323 m no 45.4

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adapt a machine, such as indicated SEALING MECHANISM FOR PACKAGING MACHINES Carl A. Frank, Hillsdale, and Joseph A. Lynch, Washingatltlxfii Township, N.J.; said Lynch assignor to said Application April 23, 1957, Serial No. 654,499 52 Claims. (Cl. 53-180) improvements in packaging machines. Packaging machines have been developed which form tubular containers from various kinds of packaging materials, fill them with a product, seal both ends of the container and discharge the filled, sealed container from the machine. Such a machine is shown, for example, in the patent to Zwoyer, No. 1,986,422. The demands of industry are constantly bringing forth newer and better materials for the improved handling and packing of old package products and the packaging of products not heretofore packaged by machine, or not satisfactorily packageable in the materials or by the machines available up to this time. The constant development of newer and better materials, therefore, makes possible the extension of machine packaging to such products which heretofore could not satisfactorily be packaged in materials such as cellophane, Pliofilm and the like.

In machines of the kind mentioned, it is possible to use, among others, plastic materials which are heat and pressure sensitive, such as cellophane, Pliofilm and others, as a packaging medium. Such materials are suitable for dry, fluent, granular or pellet type products, but are not suitable for the packaging of liquids, for example, which the industry has heretofore not been able to package satisfactorily in such flexible packaging materials in such machines.

' The heat seal made in a machine according to the patent noted above was not effective enough to hold a liquid, and the material was too easily ruptured in handling.

New developments have'recently brought forth tough, flexible, impervious materials which are strong and durable and suitable for the packaging of liquid or semiliquid materials, such as pastes, greases and the like. One such material is a polyester film made by the E. I.

This invention relates to "du Pont de Nemours & Co., known as Mylar. When formed into a tube or bag and sealed with a suitable medium, this material can efiectivelyhold a liquid such as oil or water, or a semi-liquid or paste product such as a grease, for example.

An object of the present invention, therefore, is to above, for the handling of materials of this type to form a package. More specifically, the invention deals with the method and means for effectively applying a sealing medium such as a solvent or adhesive to the material at the proper place and at the proper time in the machine cycle to seal the longitudinal and transverse edges of the tube to form a package. A seal obtained merely by heat and pressure on a heat sensitive plastic such as cellophane has been found not sufliciently effective for all purposes, but in the new material mentioned herein, heat and pressure, together with the application of a suitable sealing medium to the areas to be sealed, effectively solves the problem.

According to the invention, therefore, a roll of suittube with longitudinal overlapping edges, according to the teaching of the Zwoyer patent, and a sealing medium, such as a solvent or adhesive, is applied to one or more of the contacting faces of the overlapping longitudinal edges thereof as they are drawn through the tube former,

. prior to the heat sealing thereof which forms the tube.

The sealing medium is also applied to the interior wall of the tube so formed, but only at those portions of the tube where the transverse seal will take effect to seal the lower and upper portion of the tube to form a bag or package. The tube is then effectively shielded, according to this invention, to limit the application of the sealing medium only to those portions of the tube where the seal is to take effect and to prevent the application of the sealing medium from coming into contact with those portions of the tube which are to be occupied by the product.

Another object of the invention is to incorporate novel sealing medium feeding and applying means into the tube forming and tube feeding apparatus without otherwise I interfering with the operation of the machine.

able material is'placed in the machine, formed into a i Another object is to incorporate the invention into the product feeding tube in such manner that no change or only minor changes are needed in the machine to add such improved .tube and accessory apparatus to the machine.

A further object is to provide means for applying the sealing medium continuously to the longitudinal seam as it is formed, but only intermittently to the transverse portions of the packaging tube during the machine cycle, the application of said medium to the transverse portions of the plastic tube being synchronized with the movement of the transverse heat sealing means so that the sealing medium is applied just before the tube is clamped by the heat sealing means.

Another problem encountered in packaging machines of the kind discussed herein occurs in the packaging of fluent and powdery materials. In passing such materials through the feed tube of the machine, a rising cloud of dust is created as thematerial strikes the bottom of the newly formed envelopeor bag, and this dust settles on the inside wall of the tube or bag material where the next seal is to take place and forms a barrier to an effective seal. This problem is solved by the use of the present invention, as the mechanism described herein prevents the dust or powder from coming into contact with those portions of the packaging material where a seal will be made.

Therefore, still a further object of the invention is to provide, in a machine of this kind, an effective dust or powder shield for the packaging material as it is fed through the machine during the packaging process.

For the purpose of illustrating the invention, one embodiment thereof is shown in the accompanying drawings which are to be considered together with the following description.

In the drawings:

Figure 1 is a schematic view with parts in elevation and parts ,in section, showing the invention applied to the filler tube of a packaging machine, and showing one step in the formation of a package.

. Figure 2 is a schematic development thereof, showing a second step.

Figure 3 is a schematic development showing a third step.

Figure 4 is a' cross section taken along the line 44 of Figure 1. v

Figure 5 is a vertical, sectional view taken through the filler tube of a packaging machine, showing the invention applied thereto in section.

Figure dis a cross section taken along the line 66 of Figure 1.

3 9 Figure 7 is an enlarged elevational detail of one of the solvent applying mechanisms shown in Figure 1.

Figure 8 is an enlarged, exploded view of another of the solventapplying mechanisms shown in Figure 5.

Figure 9 is a schematic diagram showing the.'various steps in the development of a package according to this invention.

Machines of' this nature are provided with a tube former support A for the tube former B; The present support A carries a stationary outer feed tube 10 which is internally counterbored for a short distance at its upper end at 10a, Figure 5, to provide a shoulder 10b to receive and support a sleeve bearing 11. For a substantial portion of its length from its other end, this tube is similarly internally counterbored as at 100 to provide a shoulder 10d, for a purpose which will be explained.

Slidably supported within this stationary tube 10 is an inner feed tube 12 which has a collar 13' permanently fixed thereto at its upper end, the collar having a pcripheral groove 13a. At its lower end, Figures and' 8, this tube carries a feed ring 14 permanently fixed thereto, this ring having an external peripheral groove or well 14:; to receive and store a sealing; medium which is fed thereto from a tube 15, as will be more. fully explained. A flared felt applicator ring or skirt 16' encircles the feed ring and it is supported over the groove 14a by a resilient, split, snap-ring 17.

The intermediate portion of the Wall of. the inner feed tube is greater in thickness as at 12a and its ends are reduced in thickness as at 12b and 12c, providing shoulders 12d and 12e, respectively. A sleeve bearing 18, similar to the bearing 11, is supported on the reduced extension 12c and is seated against the shoulder 12e. These bearings 11 and 18 afford a smooth antifriction support for the inner tube 12 in its reciprocating movement within the sleeve 10, as will be described.

A sleeve or shield 19, Figures 5 and 8 is slidably carried on the tube 12 at its lower. end, this shield having an upper flange 19a and a lower, downwardly extending, offset skirt portion 195, the oflset being suflicient in radius to cover the flared felt applicator 16 when the latter is withdrawn into the skirt, as will be described.

The flange 19a normally rests on a stop ring 20 seated in a groove 20a formed for this purpose in the bore of .the tube at its lower extremity. A coil spring 21 is positioned in the chamber 22 between the walls of tubes 10 and 12 and is under compression between'the bearing 18 and flange 19a, normally urging the shield 19 downwardly.

Along a portion of its length the outer tube 10 may be provided with a strip 22 of heat resistant, insulating tape, such as is sold under the trademark Teflon, which may be permanently bonded to the tube or otherwise supported thereon in any suitable manner. The longitudinal seam sealing shoe, diagrammatically shown at S, such as is well known in packaging machines of this kind, seats against this strip under pressure to make the longitudinal seal when a tube is formed in the manner taught in the Zwoyer patent mentioned herein.

The tube 12 may be reciprocated with respect to the tube 10 in any desirable manner by a power take-off from the operating mechanism of the machine, but one manner of accomplishing this is diagrammatically shown in Figure 1. A cam 23, which is timed for movement in synchronization with the movement of the drawbars, operates a lever 24 through any suitable system of links and levers 25, 26. The lever 24 may be pivoted, as at 24a, at one end of a stationary part of the machine. The other end of the lever 24 is forked as. at 24b, Figure 1a, and the forked portion is suitably pivoted in the groove 13a of the collar 13. The connecting link 26 engages the lever 24 intermediate its pivot point and the forked end, and translates the rotary motion of the cam into reciprocating motion of the lever 24, which causes reciprocation of the inner feed tube 12, and the sleeve 19 carried thereby, as well as the ring 14 with its' wick;

As shown in Figure 5, the inner tube 12 and applicator ring 14 carried thereby are shown in their lower position, with the wick 16 exposed to apply the sealing medium to the interior of the plastic tube T. This corresponds to the lower position of the drawbars D in Figure 1. As the drawbar jaws open and begin to move up, the tube 12, being synchronized with. their movement, likewise moves upwardly, drawingthe wick into the shield 19b, as shown in Figure 2. As the rivets 35, Figure 5, abut against the shoulder 19c, the sleeve 19 is pulled upwardly, compressing the spring 21. When the drawbars D reach the upper limit of their stroke, close, and begin to move downwardly, the tube 12 and wick 16 move in synchronism therewith by reason of the operating mechanism as shown in Figure l, and the spring 21 forces the sleeve 19 to its starting position, with the flange 19a resting on stop ring 20a. The tube 12, however, having a longer stroke that the sleeve 19, continues to move downwardly, exposing the wick for another application of the sealing fluid to the interior of the tube T.

The sealing medium may be applied to the longitudinal edges T1, T2, Figure 6', of' the contacting facesof the tube material T as it is pulled through. the tube former B; A supply vessel 27, Figure 1, havinga. valve 28 to control the feed, is connected to the tube former by means of tubing 29 which has a wick 30" compressed in its end portion,the wick extending outwardly thereof and forming the sealing means applicator for the longitudinal seal. The wick is inserted between the overlapping walls of the tube material as shown in the detail view of Figure 7, so that it is placed in contact with the inside face of the overlapping longitudinal edges of the tube material T. As said' material is pulled past this point by the drawbars D, the sealing medium is applied to the tube material at the edges as indicated. The length of the wick is exaggerated in Figure 7 for the purpose of illustration.

The sealing medium is also supplied to the applicator ring groove 14a at the lower end ofthe tube 12 by means of flexible tubing 31 connected at one end to a supply vessel 32 which may be attached to the collar 13 in any suitable manner, as by a bracket 32a, and at its other end, the tubing is connected to the rigid tube 15, to carry the sealing medium by gravity into the groove 14a of the applicator ring.

Machines of this type are adjustable to make an envelope or bag E, Figure 9, of any desired length, within suitable limits, and we will assume, merely for the purposes of illustration, that a bag having" a length of 4" is to be made, and that the tube 12 (and therefore the wick 16) will be adjusted to have a stroke of 1".

Assuming that the machine is put into operation with the drawbars (which carry the heat sealing dies and parting'knife, all shown diagrammaticallyat D) at'the upper limit of the stroke, the tube. 12 would be correspondingly raised with the wick 16 retracted. within the skirt portion 19b of the shield 19, the shield being lifted thereby so that the flange 19a thereof. compresses the spring 21. Assuming further that a tube T of packaging material (requiring a solvent or adhesive to form an. effective seal) has been formed and has been pulled down manually to a position below thewick'16 and within thereach of the drawbars. With the vessels 32 and 27 filledwith a suitable medium for sealing, the drawbars are put into operation and the drawbars close on the end ofthe tube to make the first seal E1, Figure 9, without the application of the sealingmedium to that particular part'of'the tube, and pull the tube downwardly. This seal is ineffective and the piece will be discarded. As the drawbars reach the last quarter of the downward stroke, the tube 12, being synchronized with the movement of the drawbars, is moved downwardly to expose the'wick 16,

Figure 1, which applies a liquid sealing agent to the ina terior wall of the tube T, but only to that area E1 which forms the lower portion of the tube T and the upper edge of the first bag E, which will be discarded. The drawbars are now at the lower limit of the stroke and the relative position of the parts is shown in Figure 1, and

more clearly in Figure 9 at position a. As the drawbars reach the lower limit of the stroke, the gripping jaws open and move upwardly, preparatory to making the next seal at E2, which will be the first effective seal, the inner wall of the tube T having been moistened with the sealing medium. As the drawbars approach the upper limit of the stroke (3" movement) the wick 16 is retracted into its shield (1" movement). This is the relative position of the parts shown in Figure 2, with the drawbar D on its upward stroke. As the drawbars reach the upper limit of the stroke, the jaws close on the tube T at the area El where the tube was moistened, and form the transverse or end seal at E2. This is shown at position b, Figure 9. w

The longitudinal seam has meanwhile been prepared by the moistening of the adjacent edges of the tube T at the folding mechanism by the wick 30 as discussed above, and the seal is effected by the sealing shoe S in the manner well known in the art as the tube T is pulled forms the upper transverse portion E3 of the final package. This is illustrated at position 6, Figure 9. The

drawbars now open and release their grip on the portion 7 E2 of the completed, empty, bag E and drop it. They then move up to grip the tube T along the portion E3, which has been moistened, as shown in position a, Figure 9. As the product had already been dropped into the partially formed bag, the drawbars grip it, seal it, and sever it from the remaining upper portion of the tube along the serrated line E4, forming a completed package. This is the position of the parts shown in Figure 3. When the drawbars open to begin their upward movement to start a new cycle, the completed and filled package E drops from the machine.

Any suitable packaging material may be used on the apparatus disclosed herein, with or without the use of a sealing medium as disclosed. If the sealing medium is not desired where, for example, a seal is made by heat and pressure alone, the sealing medium is evacuated from the supply vessels 27, 32, or the valves may be closed, and a seal is made by heat and pressure alone.

It is an important feature of this invention that when it is used without the sealing medium, the felt applicator ring forms an effective dust or powder shield -to prevent dusty or powdery materials from penetrating outside the confines of the bagE as the material is dumped into it. Thefeltring 16 forms an effective barrier to the rise of dust or powder above it, and prevents such dust or powder from coming into contact with those new portions of the tube T which will subsequently form successive sealing areas.

prevents the formation of an effective seal, but with the use of the apparatus described, the problem is eliminated.

Changes may be made in the design and construction of the invention without departing from the spirit thereof as defined by the appended claims.

We claim:

1. In a packaging machine of the type which pulls a film of packaging material around the feeding tube of the machine to form a tube, fills the tube with a-product 745 said sealing medium applicator means being'synchronized The presence of such dust or powder on the walls of the material at those portionsand seals same at each end of the product to define a package, the combination comprising a feeding tube and means for supplying a sealing medium for the film material to the interior wall of said tube of packaging material at said end areas only, after said formed tube passes said feeding tube.

2. In apackaging machine of the type which'pulls a film of packaging material around the feeding tube of the machine to form a tube, fills the tube with-a product and seals same at each end of the productto define a package, the combination comprising a feeding tube and means for intermittently applying a sealingmedium 'for the film material to spaced portions of the interior wall of said formed tube as said formed tube passes said feeding tube.

3. In a packaging machine of the type which pulls a film of material around the feeding tube of the machine to form a tube, fills the tube with a product and seals same at each end of the product to define a package, the combination comprising a feeding tube and means for applying a sealing medium for said film material to the interior wall of said formed tube circumferentially thereof at said end areas only, as said formed tube passes said feeding tube.

4. In a packaging machine of the type which pulls a film of material around the feeding tube of the machine, seals the longitudinal edges of the film to form a tube, fills the tube with a product and seals same at each end of the product to define a package, the combination comprising a feeding tube, means for supplying a sealing medium for the film material to the interior wall of said feed tube, and means carried by said feeding tub e' operative to apply said sealing medium to the interior of said formed tube at said sealing areas only, as said formed tube passes said feeding tube.

5. A device according to claim 4 in which the sealing medium applicator is supported within the feeding tube.

6. A device according to claim 4 in which said sealing medium applicator comprises a wick.

7. A device according to claim 4, in which said sealing medium applicator comprises a circular wick inter- 8. In a packaging machine of the type making a tube from a film of material, filling it with a product and sealing it at each end of the product, the combination comprising a feed tube, means for forming a tube of said film of material about said feed tube, means for supplying-a sealing medium to the interior of said feed tube, and means for applying said sealing medium to those areas of said packaging material where the seals are made when said tube is formed into a package.

9. In a packaging machine of the type making a tube from a film of material, filling it with a product and-sealing it, the combination comprising a feed tube, means for forming a tube of said film material about said feed tube, means for supplying a sealing medium for said packaging material to the interior of said feed tube, means for applying said sealing medium only to those areas of said packaging material where the seals are to be' made and means for shielding from the sealing medium those areas of the packaging material which come in contact with the product.

10. In a packaging machine of the type having a feed tube around which a tube of packaging material is formed,

filled with a product and sealed at each end of the product, said machine having means for gripping and drawing said tube of packaging material and sealing it transversely, the combination comprising means for applying a sealing medium to those areas of the packaging tube gripped by the drawing means, and means for shielding the sealing medium applicator from adjacent portions of said tube, the applicator lying within the tube,

with. the movement of. the drawing means so that the sealing medium is applied as. the drawing means iscompleting its stroke.

11. In. a packaging machine of the type having a feed tube around which a tube of packaging material is formed, filled with a product and sealed at each end of the product, said. machine having means for gripping and drawing said tube of packaging material and sealing it transversely, the combination comprising means for apply- .ing a sealing medium only to those areas of the packaging tube gripped by the drawing means, and means for shielding the applicator means from adjacent portions of the tube, said shielding means being interposed between the feed tube and the tube of packaging material.

12. In a packaging machine having a feed tube and means for feeding a web of packaging material around said feed tube to form a packaging tube, the combination comprising means for applying a sealing medium to a portion of. the interior of said packaging tube as it is drawn from said feed tube, means for gripping said portion, sealing and drawing it, means to shield the package tube from said applying means while the package tube is being drawn and filled with a product, said applying means applying said sealing medium to an. area of the interior of said packaging tube above the. product just prior to. sealing said latter area.

13. In a packaging machine of the type forming a packaging tube from a moving film of material around the product feeding tube of the machine, sealing one end of the packaging tube, filling it with a product and sealing it at its other end, the combination comprising a feeding tube, means carried by the feeding tube at its lower end for applying a sealing medium to selected areas of the interior of. the packaging tube as it passes the feeding tube, and means connected to the driving mechanism of the machine for operating said applying means.

14. In a packaging machine of the type forming a packaging tube from a moving film of material around the product feeding tube of the machine, sealing one end of the packaging tube, filling it with a product and sealing it at its other end, the combination comprising a feeding tube, means on the tube for applying a sealing medium to areas above and below the product occupying area of the packaging tube as it passes the feeding tube, and means for operating said. applying means.

15. A device according to claim 14 in which the operating means is connected to the driving mechanism of the machine.

16. In a packaging machine of the type forming a packaging tube from a moving film of material around the product feeding tube of the machine, sealing one end of the packaging tube, filling it with a product and sealing it above the product, the combination comprising a feeding tube, means for pulling said packaging tube past said feedingtube, means on said feeding tube for. applying a sealing medium to areas above and below the product occupying area of. the packaging tube as it passes the feeding tube, the movement ofsaid applying means being synchronized with the movement of the pulling means so thatthe sealing medium is applied in each instance as the tube is pulled.

17. In a packaging machine having a feed tube and means for feeding a web of packaging material past said feed tube to form a packaging tube, the combination comprising means for applying a sealing medium to circumferentiahselected areas of the interior of said packagingtube as it passes beyond said feed tube.

18. A machine according to claim 17, in which said applying means is within the packaging tube.

19. A device according to claim 17, in which said applying means comprises a wick.

20. A device according to claim 17, in which said applying means comprises a wick supported by said feed tube.

' .21. A. device. according to claim. 17,. in which said.

applying means comprises a wick and means for supplying asealing medium to said wick.

22. Ina packaging machine of the type handling fluent and powdery materials, the combination comprising a feed tube, said tube adapted to support a film of packaging material as said material is folded into a packaging tube, moved past said feed tube, filled with a product and sealed; means for applying a sealing medium to the interior wall of said packaging material below said feed tube-after said packaging material is formed into a tube, and means. for gripping and pulling said packaging tube past said feed tube.

23. In a packaging machine of the type handling fluent and powdery materials, the combination comprising inner and outer feed tubes, said outer tube adapted to support a film of packaging material as said material is folded into a tube, moved past said feed tubes, filled with a product and sealed at each end, means on the inner tube for applying a sealing medium to the interior wall of said packaging material as it is formed into a tube, and means for gripping and pulling said tube past said feed tubes.

24. A packaging machine according to claim 23, in which. said applying means comprises a wick.

25. A packaging machine according to claim 23, in which said applying means comprises a wick and a sealing medium supply source, said source feeding said wick.

26. A packaging machine according to claim 23, in which said applying means comprises a wick and a sealing medium supply source, said source comprising a ring on said inner feed tube.

27. A packaging machine according to claim 26, in which; the wick is circular and is supported on said ring.

28.. A packaging machine according to claim 23, in which the sealing medium applying means is intermittently actuated to apply said medium to selected areas of said packaging material, the action of said applying means being synchronized with that of said gripping and pulling means, so that the applying means becomes operative only after the pulling of the tube has started.

29; A packaging machine according to claim 23, in which a shield is provided for said applying means, said applying means being withdrawn into said shield prior to the gripping of. said tube by said gripping and pulling means.

30. A. packaging machine according to claim 23, in which a shield is provided for said applying means, and said packaging material is intermittently shielded from said applying means.

31. A packaging machine according to claim 23, in which ashield is provided for said applying means, and said packaging material is intermittently shielded from said applying means, the operation of said shield being synchronized with the movement of said pulling means whereby the applying means becomes shielded as the pulling means moves to grip said packaging material.

32. Inv a packaging machine, the combination comprising a feed tube adapted to support a film of packaging material as said material is folded into a tube, pulled past said feed tube, filled with aproduct and sealed, reciprocable means for pulling said packaging tube, reciprocable means for applying a sealing medium to. circumferential areas of the interior wall of said packaging tube after it has been formed, and means for synchronizing the movement of said pulling means and applying means so that the sealing medium is applied as the packaging tube is pulledpast the lower end of the feed tube.

3.3.. A, device according to claim 32 in which the applying means is supported by said feed tube and reciprocates with respect thereto.

34. A device according to claim 32 in which a shield is applied to the applying device to shield same from the packaging tube during a portion of the stroke of said pulling means.

33. A device according to claim 32 in which a shield is PP i pplying device to shield same from the 9 packaging tube during a portion of the stroke of said pulling means and is actuated only as the pulling means approaches the end of its pulling stroke.

36. A dust sealing device for packaging machines handling fluent and powdery materials comprising inner and outer feed tubes, said outer tube adapted to support a film of packaging material as said material is folded into a tube and moved past said feed tubes to be formed into bags, filled with a product and sealed at each end of the product, shielding means on said inner tube movable into and out of engagement with said film tube to seal a selected area of the interior Wall of said film tube against dust caused by the discharge of a fluent material into said feed tube, and means to retract the dust shield from said film tube while said selected area of said film is moved past said shield.

37. A dust seal for packaging machines handling fluent and powdery materials comprising inner and outer feed tubes, said outer tube adapted to support a film of packaging material as said material is folded into a tube and moved past said feed tubes to be formed into bags, filled with a product and sealed at each end of the product, said inner feed tube extending below the lower extremity of said outer tube, means carried by one of said tubes to seal a selected area of said film against dust caused by the discharge of a fluent material into said inner tube, and means to shield the dust sealing means from said film while the selected of said film is moved past said shield.

38. A device according to claim 37, in which said sealing means comprises a yieldable skirt attached to said inner tube, said skirt engaging the interior wall of said tube to prevent the passage of dut particles past said skirt.

39. A device according to claim 37, in which said dust sealing means is automatically, intermittently covered by said shield.

40. A sealing means for a packaging machine comprising a feed tube, said tube adapted to support a film of packaging material as said material is folded into a packaging tube and is moved past said feed tube, and means supported within said feed tube to apply a sealing medium to selected areas of the interior of said film as it passes said feed tube.

41. A sealing means for a packaging machine comprising an outer feed tube, said tube adapted to support a film of packaging material as said material is folded into a packaging tube and is moved past said feed tube, an inner feed tube movable within said outer tube and extending below said outer tube, sealing medium applying means carried by said inner tube to apply sealing medium to said film as it is moved past said inner tube, and means for shielding said applying means from said film.

42. A sealing means according to claim 41, in which the shielding means is carried by said inner tube.

43. A sealing means according to claim 41, in which the shielding means is supported between the inner and outer tube.

44. A sealing means according to claim 41, in which the shielding means comprises'a sleeve about said inner tube with a downwardly extending skirt at its lower end, said skirt being adapted to enclose said applying means when the inner tube is raised.

45. A device according to claim 41, in which the sealing medium applicator comprises a Wick carried at the lower end of the inner tube.

46. A device according to claim 4], in which the inner tube carries a wick and means for supplying a sealing medium to said wick.

47. A device according to claim 41, in which the applying means comprises a wick support, a wick seated on said support, and a reservoir in said support for feeding said wick.

48. A device according to claim 41, in which the sealing medium applying means comprises an applicator ring fixed to said inner tube, with a wick carried by said ring, and means in said ring for feeding said wick.

49. Dust shielding means for a packaging machine comprising an outer feed tube, said tube adapted to support a film of packaging material as said material is folded into a packaging tube and is moved past said feed tube, an inner feed tube movable within said outer tube and extending below said outer tube, dust shielding means carried by said inner tube in contact with the inner wall of the packaging tube, and means for withdrawing said shield from said packaging tube.

50. The method of applying a sealing medium to a packaging tube comprising forming a packaging tube around a feed tube and moving it past said tube, and applying an adhesive to selected, circumferential areas of the interior of said packaging tube as the latter tube moves past the end of said feed tube.

5 1. The method of claim 50 in which the adhesive is applied periodically.

52. The method of applying a sealing medium to a packaging tube comprising forming a packaging tube around a feed tube and moving it past said tube, and applying an adhesive carrying wick to selected circumferential areas of the interior of said packaging tube as it moves beyond the end of said feed tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,257,823 Stokes Oct. 27, 1941 2,294,220 Albertson Aug. 25, 1942 2,419,982. Zwoyer May 6, 1947 2,766,568 Tasker Oct. 16, 1956

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