Adjustable girth former for a packaging machine

Abstract

 An adjustable girth former for a packaging machine, for continuously forming a sheet of packaging film (28) in the shape of a tube (30) advancing in a direction of forming (32). The former comprises two separate bodies (34, 36) movable relative to one another along a direction of adjustment. Each of said bodies (34, 36) comprises:

• an outer wall (34, 36) with an outer surface for guiding the film, complementary to the outer surface for guiding the film of the other body (34, 36),
• an inner wall (54, 56) with an inner surface for forming the tube, complementary to the inner surface for forming the tube of the other body (34, 36), and
• an edge for folding the film (70, 72) complementary to the edge for folding the film of the other body, the folding edge (70, 72) of each body being defined by a union line between the outer wall (38, 40) and the inner wall (54, 56).

Description

[0001] The present invention relates to machines for packaging articles in a packaging film, in particular for packaging paper rolls.

[0002] The invention refers to packaging machines in which the products to be packaged are inserted and made to advance in a tube formed by a packaging film which advances together with the products to be packaged.

[0003] The invention specifically relates to a former able continuously to form a sheet of packaging film into the shape of a tube advancing in a direction of forming.

[0004] The former has shape and dimensions that are specifically correlated to the shape and to the dimensions of the package of products. If the products to be packaged are subject to variations in dimensions as a function of the different softness of the product, variations in dimensions of the package occur which require the replacement of the former.

[0005] The document EP-A-665796 describes an adjustable girth former which allows to change the shape and the dimensions of the tube of packaging film, thereby avoiding the need to replace the former. Said adjustable girth former comprises a fixed external shell and an adjustable inner forming body. The inner forming body is so shaped as to enclose the products which move through it and it comprises opposite sections of forming elements, separated by a space with variable amplitude which extends according to an oblique angle relative to the direction of motion of the products. A lower portion of the forming body is fixed and it has flexion regions formed by longitudinal grooves defining the start of the adjustable forming sections. The adjustable forming sections must be adjusted in the horizontal and vertical direction.

[0006] The document GB 1.267.432 discloses an adjustable former comprising two lateral walls, movable relative to one another to vary the width of the tube of packaging film. The former described in this document approaches the longitudinal end edges of the film to each other, forming a continuous rib which extends on the exterior of the film. This type of former is not able to superpose the longitudinal edges of the sheet to each other in such a way as to form a package without external projections.

[0007] The object of the present invention is to provide an adjustable girth former which allows to form a continuous tube of film with superposed edges and which has a high precision of adjustment of the dimensions of the tube of film with a simple adjustment motion.

[0008] According to the present invention, said object is reached by an adjustable girth former having the characteristics set out in claim 1. Preferred embodiments of the invention according to the invention are claimed in the dependent claims.

[0009] The characteristics and advantages of the present invention shall become readily apparent in the detailed description that follows, provided purely by way of non limiting example, with reference to the accompanying drawings in which:

• Figure 1 is a schematic perspective view of a part of a packaging machine provided with a former according to the present invention,
• Figures 2 and 3 are perspective views of the former according to the invention in two working positions,
• Figure 4 is a plan view showing the two separate bodies constituting the former according to the invention,
• Figure 5 is a view according to the arrow V of Figure 4, and
• Figures 6 and 7 are schematic sections showing the former according to the present invention in the working positions of Figures 2 and 3, respectively.

[0010] With reference to Figure 1, the number 10 designates a former according to the present invention, to be used in a packaging machine to package paper rolls in a film of plastic material.

[0011] The packaging machine comprises an assembly for feeding products 12 arranged to make groups of products to be packaged 14 advance in a horizontal direction indicated by the arrow 16. The assembly for feeding the products 12 is provided with known means (not shown) to make the groups of products 14 advance in the direction 16. The feeding assembly 12 is also provided with an adjustable guiding device 18 which guides the groups of products 14 towards the inlet section of the former 10. The guiding device 18 is adjustable in the direction transverse to the direction of advance 16 of the groups of products 14 as schematically indicated by the double arrows 20 in Figure 1.

[0012] The former 10 comprises an outer shell 22 and an inner forming element 24. The outer shell 22 and the inner forming element 24 define a folding edge 26. In operation, a sheet 28 of film of packaging material is guided on the outer surface of the outer shell 22 and is folded on the folding edge 26. The film remains adherent to the inner surface of the forming element 24 and it forms a continuous tube 30 which advances in a direction of forming 32 coinciding with the longitudinal axis of the forming element 24. In the continuous tube 30 the longitudinal edges of the sheet 28 are mutually superposed in such a way that the tube has no film edges projecting on its outer part.

[0013] The former 10 according to the present invention is adjustable to vary the dimension of the tube 10 in transverse direction relative to the direction of forming 32. With reference in particular to Figures 4 and 5, the former 10 comprises two mutually separate and independent bodies 34, 36 constituted by sheet metal.

[0014] Each of the two bodies 34, 36 comprises a respective outer wall 38, 40 whose outer surface forms a surface for guiding the film, complementary to the outer surface of the other body. The set of the two outer walls 38, 40 forms the outer shell 22 of the former 10. Each outer wall 38, 40 has a planar lower surface 42, 44, a planar upper portion 46, 48 parallel to the respective lower portion 42, 44 and a curved portion 50, 52 which joins the two planar portions 42, 46 and 44, 48 to each other. The curved portion 50, 52 of each body 34, 36 is tapered towards the front part of the former.

[0015] Each body 34, 36 has a respective inner wall 54, 56 with an inner surface for forming the tube, complementary to the inner surface of the other body. The set of the inner walls 54, 56 of the two bodies 34, 36 constitutes the forming element 24 of the former 10. The inner wall 54, 56 of each body 34, 36 comprises a planar lower portion 58, 60, a planar upper portion 62, 64 and an arched portion 66, 68 which mutually joins the planar portions 58, 62 and 60, 64.

[0016] The inner wall 54, 56 of each body 34, 36 is permanently fastened to the outer wall 38, 40 of the same body. The portions of inner wall 58, 60, 66, 68, 62, 64 and the portions of outer wall 42, 44, 50, 52 and 46, 48 are fastened to each other or are obtained starting from a single sheet of bent sheet metal. The portions of inner and outer wall are essentially rigid and non deformable.

[0017] The inner wall 54, 56 of each body 34, 36 is joined to the corresponding outer wall 38, 40 along a folding edge 70, 72 complementary to the folding edge of the other body. The set of the edges 70, 72 of the two bodies 34, 36 constitutes the folding edge of the film 26 of the former 10. The folding edge 70, 72 of each body 34, 36 has a lower rectilinear segment 74, 76, transverse relative to the direction of forming 32, an upper rectilinear segment 78, 80 inclined relative to the direction of forming 34 and an arched segment 82, 84 which mutually joins the rectilinear segments 74, 78 and 76, 80.

[0018] The upper rectilinear segments 78, 80 of the folding edges 70, 72 of the two bodies 34, 36 have opposite inclination relative to the direction of forming and intersect each other according to a general V configuration.

[0019] The two bodies 34, 36 are movable relative to each other along a transverse direction relative to the direction of forming 32. Preferably, the two bodies 34, 36 are provided with guiding means, mutually co-operating to guide the relative motion between the two bodies 34, 36 in the direction orthogonal to the direction of forming 32. In the example illustrated in Figures 4 and 5, the guiding means comprise two pivot and slit guides. A first guide is provided at the lower portions 42, 44 of the outer walls 38, 40 and a second guide is positioned at the upper portions 46, 48 of the outer surfaces 38, 40. The first guide comprises a plate 86 fastened to the portion 42 of the first body 34 and provided with two guide grooves 88 engageable by respective guide pivots 90 fastened to the portion 44 of the body 36. The second guide comprises an arm 92 fastened to the portion 46 of the first body 34 and bearing a plate 94 provided with a guide groove 96 engageable by a pivot pin 98 fastened to the portion 48 of the body 36.

[0020] With reference to Figures 2 and 3, the former 10 according to the present invention is associated to an adjustment device 100 to vary the relative position between the bodies 34, 36 in a direction orthogonal to the direction of forming 32. In the illustrated example, the adjustment device 100 comprises a threaded rod 102 driven in rotation by an electric motor (not shown). The threaded rod 102 has two threaded segments with opposite thread which engage respective blocks 104, 106 each of which is fastened to a respective body 34, 36 through an arm 108, 110. Figures 2 and 3 schematically show two operative positions of the former 10.

[0021] The adjustment of the former 10 can be effected automatically on the basis of information about the softness of the products to be packaged. A particularly simple way to measure the softness of the products consists of measuring the current absorbed by the electric motors which drive the advance of the products 14 towards the inlet of the former 10.

[0022] Figures 6 and 7 schematically show two paper rolls 14 inserted in the forming element 24 of the former according to the invention. Figure 6 shows the position of the forming element 24 with rolls 14 of minimum diameter, corresponding to the configuration of Figure 2. Figure 7 shows the position of the forming element 24 with rolls 14 of maximum diameter, corresponding to the configuration of Figure 3.

[0023] In the configuration of Figure 7, the rolls 14 have an outer diameter substantially equal to the diameter of curvature of the curved portions 66 of the inner walls 54, 56. In this configuration, the outer surfaces of the rolls are in contact with the respective curved portions 66, 68 along an arc with an extension substantially equal to the angular extension of the curved portions 66, 68.

[0024] With rolls 14 having a smaller diameter than the diameter of the curved walls 66, 68, each of the rolls 14 would touch the curved portions 66, 68 only in one point. To obtain a more extensive contact surface with the curved walls 66, 68, the rolls 14 are compressed in the transverse direction between the curved portions 66, 68. As a result of this compression, the rolls 14 are deformed and assume a slightly oval shape, as shown schematically in Figure 6. Thanks to the deformation of the rolls 14, also in this case the rolls 14 are in contact with the curved portions 66, 68 along an arc whose extension is substantially equal to the angular extension of the curved portions 66, 68.

Claims

1. An adjustable girth former for a packaging machine, for continuously forming a sheet of packaging film (28) in the shape of a tube (30) advancing in a direction of forming (32), characterised in that it comprises two separate bodies (34, 36) movable relative to one another along a direction of adjustment, each of said bodies (34, 36) comprising:

- an outer wall (34, 36) with an outer surface for guiding the film, complementary to the outer surface for guiding the film of the other body (34, 36),

- an inner wall (54, 56) with an inner surface for forming the tube, complementary to the inner surface for forming the tube of the other body (34, 36), and

- an edge for folding the film (70, 72) complementary to the edge for folding the film of the other body, the folding edge (70, 72) of each body being defined by a union line between the outer wall (38, 40) and the inner wall (54, 56).

2. Former as claimed in claim 1, characterised in that the outer wall(38, 40) of each of said bodies (34, 36) comprises a planar lower portion (42, 44), a planar upper portion (46, 48) and a curved portion (50, 52) which mutually joins the planar portions (42, 46), the curved portions (50, 52) being tapered towards the front part of the former (10).

3. Former as claimed in claim 1, characterised in that the inner wall (54, 56) of each body (34, 36) comprises a lower planar portion (58, 60), an upper planar portion (62, 64) and a curved portion (54, 56) which mutually joins said planar portions (58, 62, 60, 64).

4. Former as claimed in claim 1, characterised in that the folding edge (70, 72) of each body (34, 36) comprises a rectilinear lower segment (74, 76) orthogonal to the direction of forming (32), an upper rectilinear segment (78, 80) inclined relative to the direction of forming (32) and a curved segment (82, 84) which joins the rectilinear segments to each other (74, 78, 76, 80).

5. Former as claimed in claim 4, characterised in that the upper rectilinear segments (78, 80) of the folding edges (70, 72) of the two bodies (34, 36) have opposite inclination relative to the direction of forming (32) and intersect each other according to a general V configuration.

6. Former as claimed in claim 1, characterised in that the first and the second body (34, 36) are provided with mutually co-operating guiding means (88, 90, 96, 98).

7. Former as claimed in claim 1, characterised in that the two bodies (34, 36) are associated with an adjustment device (100) including a threaded rod (102) engaging two blocks (104, 106) each of which is fastened to a respective body (34, 36).

8. Former as claimed in claim 7, characterised in that the adjustment device (100) is operated according to information about the softness of the products to be packaged.

9. Former as claimed in claim 8, characterised in that the information about the softness of the products to be packaged is provided by a measure of the current absorption of electrical motors that feed the products (14) to the former (10).

Drawing