ES2370444T3 - APPARATUS TO FIX AN EXTREMITY OF A STRIP OF WRAPPING MATERIAL IN A MACHINE TO WRAP PRODUCTS. - Google Patents

Abstract

An apparatus (1) for a product (3) wrapping machine (2) comprises: a first elongated element (7), supported by the machine (2) structure (8), being movable in such a way that a continuous strip (5) of wrapping material can be wrapped around both the first elongated element and the product (3) which is in turn wrapped in a preformed wrapper (4); an operating unit (9) having a reel (10) of adhesive tape, from which an end stretch (11) of tape is unwound and stably held flat in front of the first elongated element (7) and with an end (6) of the strip (5) of wrapping material inserted between them. The apparatus (1) also includes presser means (12; 25, 43, 45) and means (13; 46, 47) for moving the operating unit (9) against the wrapper (4) in contact with the first elongated element (7) and cutting means (23; 24) for cutting the adhesive tape from the relative feed reel (10) when said tape is fixed to the wrapper (4).

Description

Apparatus for fixing one end of a strip of wrapping material in a machine for wrapping products

Technical Field

The present invention relates to the automated product wrapping sector in which wrapping machines form, around the products, containment and protection wrappings obtained by wrapping several times a continuous strip of wrapping material around the same products. The present invention relates to an apparatus for attaching, by adhesion, one end of the strip of wrapping material to the wrapper, at the end of the wrapping.

Existing Technique

There are apparatuses belonging to the technique known for the wrapping technique mentioned above, which fix the end of the strip of wrapping material by means of a succession of stages that involve:

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 the formation of a special pocket in the wrapper, taking advantage of the elasticity of the film material and the help of some mechanical elements that intervene during the wrapping;

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 the introduction of the end of the strip of wrapping material into said pocket and then released there; Y

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 the release of the wrapping band by the mechanical elements, so that, due to the elastic return of the material with which the strip is made, the pocket closes on itself, gripping the end of the wrapping band, the which, therefore, is definitively fixed to the packaging. In the document RN2006A000066 belonging to the same requesting party, for example, the description of such a known technique can be found.

US 2006 / 0.272.286 discloses a machine for applying an adhesive tape to be used with an elastic wrap. This machine comprises a mechanism for applying the adhesive tape, which applies the adhesive tape when it is pressed against an object and displaced with respect to the same object.

The known technique described above has provided totally satisfactory practical results. However, it is subject to improvements at least as regards: reduction of the complexity of the fixing process; reduction of the complexity of the devices that carry out such a process; and general reduction of operating cycle times.

Disclosure of the Invention

The main objectives of the present invention, therefore, are to provide a simplification of the fixing process; provide a simplification of the devices used to carry out said process; and provide shorter operating cycles, at least as far as fixing operations are concerned. All this to allow savings with respect to the process; savings with respect to the manufacture of the devices; and increase its level of reliability in comparison with the apparatus of the known technique, considering the possibility that such machines and apparatus can be used in packaging lines with high operating speed and / or continuous cycle, that is under difficult operating conditions.

The present invention, in accordance with said objectives, exhibits clearly deductible technical characteristics from the appended claims, in particular claim 1, and in any of the claims directly or indirectly dependent on claim 1.

Brief Description of the Drawings

The advantages of the present invention are further demonstrated in the detailed description that follows, with reference to the accompanying drawings illustrating preferred and non-limiting embodiments of the invention, in which:

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 Figure 1 is a diagram of a wrapping machine provided with an apparatus in accordance with the present invention, shown in a non-operative condition;

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 Figure 2 is a partial perspective view of a wrapping machine provided with the apparatus in accordance with the present invention, shown in a first stage of transition to an operational condition;

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 Figure 3 is a view of the machine in which the apparatus is getting closer to the operating condition;

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 Figure 4 is an enlarged view of the apparatus corresponding to that of Figure 3;

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 Figure 5 is a partial view of the machine of Figure 1, with some parts omitted to better illustrate some functional aspects;

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 Figure 6 is a view of the machine in which the apparatus is in the operative condition;

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 Figure 7 is an enlarged view of the machine corresponding to that of Figure 6;

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 Figure 8 is a diagram of the principle of operation of a special component part of the apparatus;

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 Figure 9 is a partial perspective view of the machine of Figure 1, showing the apparatus at a stage characteristic of its operating condition;

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 Figure 10 is an enlarged partial perspective view of the machine of Figure 9, viewed from a different point of view and illustrated in its operational condition;

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 Figure 11 is a detailed perspective and enlarged view of a part of the apparatus according to the present invention;

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 Figure 12 is a detailed perspective and enlarged view of a part of the apparatus according to the present invention, seen from a different point of view than that of Figure 11;

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 Figure 13 is a detailed perspective and enlarged view of a part of the apparatus according to the present invention, during a significant operational stage;

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 Figure 14 is a perspective view corresponding to that of Figure 13, showing an operating condition of the successive apparatus to that of Figure 13.

Detailed Description of the Preferred Executions of the Invention

With reference to Figure 1 of the attached drawings, the number 2 denotes a conventional wrapping machine, in its entirety, for packaging products (3) - arranged, for example, in the form of a vertical stack - within a wrapper. The wrapper (4) is formed by the machine (2) directly on the products (3) gradually and repeatedly wrapping the same products (3) with a continuous strip (5) of wrapping material, which is composed, for example, of a long film of plastic material, which can stretch elastically.

More particularly, the wrapping machine (2) has [figure 2] a vertical frame (37) and a horizontal ring structure (8) which: is inside the frame (37); and can move along a guide lengthwise with respect to the vertical part of the frame (37). The annular structure (8) supports means (35) for distributing the continuous strip (5) of wrapping material, said means being able to move through the annular structure (8) and being driven so that they can describe a corresponding circular path.

The products (3) to be wrapped, supported on a horizontal platform, or an equivalent roller plane, are placed inside the frame (37), substantially centered with respect to the latter, that is to say in a substantially central position with respect to the structure cancel (8).

The distribution of the strip (5) through the distributing means (35) during its circular movement and the simultaneous movement of the annular structure (8), properly composed and coordinated so as to be kinematically synchronized, cause repeated wrapping operations with the strip (5) of wrapping material, in reciprocal succession, thus forming a wrapper (4) on the products (3) by wrapping [figure 4].

Returning to Figures 1 and 2, it should be noted that the annular structure (8) supports an apparatus, denoted with the number 1 in its entirety, to fix the wrapper (4), at the end of the wrapper, and using methods that will be described then, one end (6) [figure 4] of the strip (5) of wrapping material, so as to definitively close the wrap (4) on the products (3) at the end of the wrap.

The apparatus (1), which is the specific object of the present invention, basically comprises: a first elongate element, denoted in its entirety with the number 7; an operating unit, denoted by the number 9; (as shown more clearly in Figures 10 and 11) Pressing means and movement means of the operating unit (9), denoted in their entirety with numbers 12 and 13 respectively; and a clamp, denoted in its entirety with the number 32.

The first elongate element (7) is supported in such a way that it protrudes in a cantilever manner from the annular structure (8) of the machine (2) by work of structural elements not exhibited for reasons of clarity. It has the shape of a parallelepiped with a polygonal, quadrangular contour, and a hollow tubular structure.

In particular, preferably said first elongate element (7) is composed of two separate component parts (16 and 17), arranged coaxially and in reciprocal guidance. Said parts (16 and 17) can move axially in reciprocal relationship, whereby the first elongate element (7) becomes telescopic under activation of suitable actuators not shown in the drawings, for example housed in the tubular cavity.

The first elongate element (7) has a first end (36) hinged on a fixed part of the annular structure (8) of the machine (2), and a second opposite end (38) free of projecting overhang of the structure cancel (8). The hinged limb (36) has an arm (39). Actuators not shown, properly connected to the arm (39) and acting on it, allow the first element (7) to be inclined by rotating it around the hinge axis between two limit positions, separated from an angle of approximately 90 ° and appreciable clearly comparing figures 1 and 2.

More particularly, in one of said limit positions the first elongate element (7) is in the non-operative condition, arranged horizontally and substantially within the vertical space occupied by the annular structure (8). On the contrary, in the other position, the first elongate element (7) is inclined so as to be arranged vertically, projecting downwardly in a cantilever manner and being located in the space in a substantially intermediate position between the products (3) and the means (35) for distributing the strip (5) of wrapping material, the latter means, in turn, being supported by the annular structure (8) near its perimeter, as can be seen, for example, in the figures 3 and 4.

A second elongated element (27), also with a tubular parallelepiped structure, has a first end (40) hinged on the annular structure (8) and supports the operating unit (9) in correspondence of its second free end (42). The second element (27) also has an arm (41) for connecting an actuator element not shown in the drawings. The activation of the arm (41) allows the second elongated element (27) to rotate around its hinge point and extend to a certain angle and parallel with the first elongated element

(7) between the limit positions, which substantially correspond to those of the first elongate element (7).

Figure 1 shows how in its non-operative condition, the second elongate element (27) is oriented horizontally and is arranged on a vertical plane, substantially parallel with a corresponding plane containing the first elongated element (7). Then, the second elongated element (27) with a rotation of 90 ° [Figure 7] is brought to its operational condition so that its operating unit (9) can be placed against a flat face (15) of the first elongated element (7) .

The operating unit (9) supported by the second elongate element (27) comprises in particular [figures 11, 12 and 13]: a flange (43), which supports a bolt (44) that supports a coil (10) in a cantilever manner. of adhesive tape. The operating unit (9) also has a support surface (18) with which depression means (19) are associated, the latter including a depression chamber (20) behind the surface (18) and in communication with the environment external circumstance through through holes (21), which pass through the surface (18).

Also, the operating unit (9) includes a pair of rollers (22) that rotate madly around their rotation axes, located respectively parallel to each other on two opposite sides of the support surface (18).

Likewise, the operating unit (9) includes second cutting means (23) comprising a blade (24) arranged adjacent to the support surface (18), which can be moved, under control, transversely to said surface (18) between a non-operative position, behind the surface (18) and folded in the unit (9), and an operational position, advanced with respect to the surface (18). Advantageously, the blade (24) can be actuated by means of a linear single acting actuator, which in its idle state keeps the blade (24) in the backward position and in its activation state, on the contrary, it causes the blade (24) moves beyond said surface (18).

A terminal section (11) of the adhesive tape coming from the reel (10), after having been unwound from the same reel (10), passes around the rollers (22) positioning in correspondence of a point tangent to them and in a point tangent to the surface (18) arranged between them. Therefore, when the unit (9) is in the operating condition shown in Figures 6 and 7 the terminal section (11) is supported by the same operating unit

(9) plane facing the face (15) of the first elongate element (7).

The flange (43) of the operating unit (9) is placed on a first linear guide (25), rectilinear and substantially at right angles to the face (15) of the first elongate element (7). Said connection of the flange (43) and the guide (25) allows the operating unit (9) to move with respect to the first elongate element (7) so as to approach or move away from it, when suitable actuator means (45) are activated. ) [clearly shown in figure 10]. Therefore, the flange (43), the guide (25) and the respective actuator means (45) form a kind of exemplary and more specific embodiment of the pressing means (12) defined above in more general terms.

The attached drawings also show how the second elongate element (27) also comprises two separate component parts (46 and 47), whose contour is polygonal, which are coaxially connected, one guided over the other, so as to also make the Second element (27) is telescopic under activation of an actuator, not visible in the drawings, for example housed in the same second elongated element (27). In practice, said execution of the second element (27) forms a second guide (26) that provides a specific and specific exemplary execution of movement means (13) suitable to allow the operating unit (9) to move with respect to the first element elongated (7), longitudinally and parallel to its face (15).

On the other hand, Figure 5 shows means (14) for compacting the continuous strip (5) of wrapping material in the plane in which it is arranged forcing the longitudinal edges (49 and 50) of the same strip (5) to approach each other. . Preferably, said means (14) are associated with means (35) for distributing the strip (5) of wrapping material and comprise: a pair of adjacent rollers (28) transverse to the opposite longitudinal edges (49 and 50) of the strip (5); a pair of spiral nuts (29), each holding a roller (28); and a motorized shaft (30) with threads in opposite directions, on which the spiral nuts (29) are linked. It follows that the rotation of the shaft (30) causes movements in opposite directions of the two spiral nuts that, when moving in reciprocal approach, cause the rollers (28) to push against the edges (49 and 50) of the strip (5) with corresponding reduction of its reciprocal distance, thus compacting the strip (5) of wrapping material in its own layout plane.

As indicated above, the apparatus (1) has a clamp for the strip (5), denoted in its entirety with the number 32, which in particular comprises two flat jaws (32a and 32b) parallel and facing each other and in conditions of moving in reciprocal relationship thanks to a linear guide (63). The clamp (5) also includes cutting means, denoted in its entirety with the number 34.

In particular, Figures 11, 12 and 13 show that the cutting means (34) comprise a blade (57) supported by a plate (58) mounted so that it can move guided by two parallel rods (59) fixed to one of the jaws (32a). Two springs (60) coaxially placed on the rods (59), interact on one side with the jaw (32a) and on the other side with the plate (58), pushing the blade towards a position away from the jaw denoted with 32a. The activation of a linear actuator (61), connected to the plate (58), causes the blade (57) to be pushed against the reaction of the springs (60), causing it to move first towards the jaw (32a) and then coming out of the jaws (32a and 32b) through a pair of grooves (62a and 62b) made correspondingly therein in a position facing the blade (57).

Figure 7 and the diagram of Figure 8 show how the apparatus (1) can also comprise a roller (51), movable and motorized. The roller (51) is housed at a spatial angle (55) bounded on one side by the wrapper (4) and on the other side by the end (6) of the strip (5) and with its vertex (56) substantially associated with the first elongated element (7). The roller (51), as will be described in details below, can be moved so that it is located parallel with the elongate elements (7 and 27) and in a suitable position with respect to the continuous path of the continuous strip (5 ) of the wrapping material that extends from the distribution means (35) in order to facilitate an optimal and safe fastening of the strip (5) by the clamp (32).

Next, the operation of the wrapping machine (2) and the respective apparatus (1) will be described starting with the initial condition of the machine (2) corresponding to Figure 1, in which a generic product (3) to be wrapped and it is disposed within the frame (37) and substantially centered with the vertical central axis (3a) of the same frame. The apparatus (1), as a whole, is oriented horizontally - in the non-operative condition - within the vertical space occupied by the horizontal annular structure (8). When the annular structure moves and the distribution means (35) of the strip (5) of wrapping material rotate on said structure, the wrapper (4) is generated as a succession of turns that gradually wrap the product (3) and they tighten it around due to the tension they apply and the elasticity of the material with which the strip is made.

Before finishing the wrapping, that is to say before depositing a predetermined amount of terminal turns of the wrapping (4), the first elongate element (7) is given a command to move to a position parallel to the axis (3a) [Figure 2 ] and it is also extended axially of a length chosen according to the characteristics of the wrapper to be made [figure 3]. The continuation of the wrap determines that the first elongate element (7) is wrapped together with the product (3) for a predetermined number of turns. Therefore [Figure 4], some of said final turns of the wrapper (4) being formed pressed against the face (15) of the first elongate element (7) are separated from the turns previously pressed on the product (3), from which are separated by a kind of separating air space (52), substantially between the first elongate element (7) and the product disposed on its back. It should be noted that due to the distance between the product (3) and the first elongated element (7), maintaining the same wrapping conditions, the turns that also wrap the first elongated element (7) have a dilated circumference compared to those already deposited in direct contact with the product (3).

As the envelope [figure 6] follows, the parts (16 and 17) of the first elongate element (7) slide axially with respect to each other and the second elongate element (27) is rotated 90 ° and brought in front to the first elongated element (7). Figure 7 shows how the end (6) of the strip (5) of wrapping material, for the final part that wraps the first elongate element (7), is located in an intermediate position between the two elongated elements (7 and 27). In addition, Figure 9 shows how, successively, the second elongate element (27) is disassembled, therefore having its component parts (46 and 47) arranged in reciprocal succession.

Meanwhile, the operating unit (9) is still located distant from the first elongated element (7) and holds the section (11) of adhesive tape against the face (15) of the elongate tape, which the rollers (22) and the surface (18) and which is held in a stable position in front of them by means of a depression through the holes (21) made in the surface (18).

Then, the unit (9) [figure 10] is moved forward along the first guide (25), moving towards the end (6) of the strip (5) of wrapping material, until it comes into contact with the face (15) of the first elongate element (7). Said advance movement brings the operating unit (9) to the conditions shown in Figure 11, where adhesion to the wrapper (4) of an initial part of the initial section of the adhesive tape is caused.

A subsequent command sent to the second elongated element (27) causes the part denoted with 47 to move with respect to the part denoted with 46 of the second elongated element (27) while the operating unit (9) continues to unwind the strip (11) of Adhesive tape of the coil (10) and stretches the bridge over the end (6) of the continuous strip (5) of wrapping material.

While this movement is being carried out, the clamp (32), connected to the flange (43), surrounds the extremity (6), of three sides, with its open jaws (32a and 32b), as can be seen in the figure eleven.

At the end of the retraction stage of the second elongate element (27), the clamp (32) squeezes the jaws (32a and 32b) onto the limb (6); then to the blade (57) of the respective cutting means (34) is sent the command to move forward through the grooves (62a and 62b), so as to cut the strip (5) of wrapping material, of which, as can be seen in Figure 13, the part closest to the film coil (53) is supported by the clamp (32), and the furthest part is fixed to the wrapper (4) by the section (11 ) of adhesive tape still connected to its distribution coil (10).

Then, while the product (3) has been permanently wrapped and while the continuous strip (5) of wrapping material is retained by the clamp (32), making movements opposite to those described above, the apparatus

(1) returns to the condition shown in Figure 1 ready to begin a new wrapping cycle. It should be noted that after the first elongate element (7) has been axially retracted, if necessary accompanied by a movement of the annular structure (8) towards the top of the frame (37), when the first elongated element (7) leaves the air space (52), the turns of the envelope (4) relative to said air space (52) are tight, due to its elasticity, firmly on the product (3) as a result of the discharge of the accumulated elastic energy in advance

Turning to Figure 14, it should be noted that to fix the wrapper (4) with a section (11) of minimum length of adhesive tape, before the apparatus (1) the means (35) to distribute the strip (5) of wrapping material by compacting the strip (5) of wrapping material in its layout plane, as can be seen in figure 5.

As said figure clearly shows, before the intervention of the apparatus (1) the end (6) of continuous strip (5) of wrapping material is contracted in its arrangement plane by the effect of the rollers (28) that as a consequence of having been properly forced to turn the shaft (30) on the other hand, they are moved forward in opposite directions from each other by the spiral nuts (29) that support them.

It should be noted that the compaction of the strip (5) before fixing it to the wrapper (4) with the section (11) of adhesive tape, as well as the advantage of reducing the amount of adhesive tape necessary for wrapping operations, offers the additional advantage of limiting the maximum axial travel of the component parts (46 and 47) of the second elongate element (27), providing greater simplification, in terms of construction, of execution of the movement means (13). In addition, by globally reducing the operational paths of the moving parts of the apparatus (1) an acceleration of the respective wrapping cycles is achieved.

Figure 8 shows how for some product dimensions (3) and due to a strictly geometric problem there may be cases where the end (6) of the strip (5) of wrapping material is too close to the terminal turns of the wrapper (4) that precede it.

If you had to face that case, during operation of the device (1) the clamp (32) may not be able to place its jaws (32a and 32b) only around the limb (6), since it also It could interfere with the wrapping turns (4).

To prevent the above, the presence of the roller (51) and its pressure against the wrapper (4), also facilitated by the elasticity of the material, allows the end (6) of the strip (5) of wrapping material to come clearly deflected with respect to the preceding wrapping turns, expanding the spatial angle (55) in which the roller (51) is housed, that is, guaranteeing the conditions for a totally certain and regular wrapping of the end of the wrapper (4) by the clamp (32), whatever the effective dimensions of the product (3) to be wrapped.

The invention just described is susceptible of obvious industrial application. In addition, the invention can be adapted or modified in several ways without thereby departing from the scope of the inventive concept.

Among the many alternative executions, one can be represented by way of example by elongated elements (7 and 27) that have a non-tubular shape, which for example in an equivalent manner could even be that of an open box configured in U.

In addition, all the details of the present invention can be replaced by technically equivalent elements.

Claims (15)

1.- Apparatus for wrapping products (3) with a wrapper (4) created by wrapping the products (3) by wrap around them of a continuous strip (5) of wrapping material distributed from a respective coil (53); the apparatus (1) having first cutting means (34) for separating from the coil (53) one end (6) of the strip (5) of wrapping material and being suitable for fixing said end (6) to the wrapper (4) ) at the end of the envelope, the apparatus (1) being characterized by the fact that it comprises:

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 a first elongate element (7), supported by the structure (8) of the machine (2), with the possibility of moving between a non-operative condition with respect to the wrap of the products (3) and an operative condition, in the which continuous strip (5) is wrapped around the first elongate element (7) together with the product (3);

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 an operating unit (9) with a coil (10) of adhesive tape, from which a section (11) of adhesive tape is unwound, being held so as to be arranged flat in front of the first elongate element (7), the strip (5) of wrapping material being introduced between the section (11) and the first elongate element (7);

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 pressing means (12; 25, 43, 45) suitable for pressing the operating unit (9) against the casing (4) in contact with the first elongate element (7);

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 movement means (13; 46, 47) suitable for imparting to the operating unit (9) a movement along a direction transverse to the wrap direction of the continuous strip (5) of wrapping material; Y

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 second cutting means (23; 24) for cutting the terminal section (11) of adhesive tape and separating it from the distribution coil (10).

2. Apparatus according to claim 1, characterized in that it comprises means (14; 28, 29, 30) for compacting the strip (5) of wrapping material in its arrangement plane, moving its longitudinal edges (49, 50 ) in reciprocal approach. 3. Apparatus according to claim 1, characterized in that the first elongate element (7) is hinged in a structure (8) of a wrapping machine (2), so that it can move at a certain angle with respect to the product (3) and, therefore, can be oriented for the operational or non-operational condition. 4. Apparatus according to claim 1 or 3, characterized in that the first elongate element (7) has a telescopic structure, suitable to allow the same first elongate element (7) to have selectively variable lengths depending on the needs of wrapping , said first elongate element (7) comprising at least two coaxial parts (16 and 17), able to move in reciprocal relationship, one guided over the other, and at least one flat face (15) facing the operating unit (9) and substantially parallel with the terminal section (11) of the adhesive tape distributed from the coil (10). 5. Apparatus according to claim 1, characterized in that the operating unit (9) has a surface (18) that supports the terminal section (11) of adhesive tape, and depression means (19; 20, 21), associated with the surface (18) and suitable for holding the terminal section (11) of adhesive tape in direct contact with the surface (18), said operating unit (9) including a pair of rollers (22), which can rotate crazy about of their rotation axes, located on both sides of the support surface (18) respectively and suitable for subtending the terminal section (11) of adhesive tape so that it faces the support surface (18). 6. Apparatus according to claim 9, characterized in that the depression means (19; 20, 21) include a vacuum chamber (20), behind the surface (18) and in communication with the terminal section (11 ) of adhesive tape by means of holes (21) passing through said surface (18). 7. Apparatus according to claim 1, characterized in that the cutting means (23; 24) include a blade (24), with monodirectional activation commanded, which when activated is brought to a position adjacent to said surface (18 ) which supports the terminal section (11) of adhesive tape. 8. Apparatus according to claim 1, characterized in that the pressing means (12; 25, 43, 45) include at least a first guide (25) oriented transversely with respect to the first elongate element (7) when this the latter is in its operational condition with respect to the products (3); the first guide (25) supporting the operating unit (9) in a condition in which it can move in both directions allowing the same operating unit (9) to move in and out of the first elongate element (7); the pressing means (12; 25, 43, 45) including actuator elements (45) for pushing the operating unit (9) against the first elongate element (7), or vice versa, to move the operating unit away from the latter. 9. Apparatus according to claim 1, characterized in that the movement means (13; 46, 47) include a second guide (26) oriented parallel to the first elongate element (7) when the latter is in its operative condition ; the second guide (26) supporting the operating unit (9) in a condition in which it can move in both directions allowing a parallel movement with the first elongate element (7); the movement means (13; 46, 47) including actuator elements to drive the operating unit (9) with respect to the second guide (26) and a second elongate element (27) comprising coaxial parts (46, 47) that can move in reciprocal relationship, parallel with the first elongate element (7), so as to form the second guide (26) for the movement of the operating unit (9), said second elongate element (27) being hinged in the structure (8 ) of the wrapping machine (2) so that it can move up to a certain angle with respect to the product (3) and, therefore, can be oriented for a non-operative condition distant from the products (3) and vice versa for a condition operational in which it is close to the same products (3). 10. Apparatus according to claim 2, characterized in that the means (14; 28, 29, 30) for compacting the end (6) of the strip (5) of wrapping material include a pair of rollers (28) ; a pair of spiral nuts (29), each supporting a roller, respectively, belonging to said pair according to an angle that is transverse to the longitudinal edges (49 and 50) of the strip (5) of wrapping material; and a single motorized shaft (30) with which the spiral nuts (29) are coupled, the rotation of the shaft (30) causing the spiral nuts (29) to move in opposite directions to each other, suitable for determining, when they move in reciprocal approach, the action of the rollers (28) against the longitudinal edges (49 and 50) of the strip (5) of wrapping material and the consequent compaction of the strip (5) in its arrangement plane. 11. Apparatus according to claim 1, characterized in that the operating unit (9) includes at least one clip (32) for holding and retaining the end (6) of the strip (5) of wrapping material during the product wrap (3), said clip (32) being supported by the operating unit (9). 12. Apparatus according to any one of the preceding claims, characterized in that it comprises a roller (51) suitable to be inserted between part of the wrapper (4) already formed on the product (3) and the end (6) of the strip (5) that is still being unwound from the respective coil (53), the roller (51) being able to move between said part of the wrapper (4) and said end (6) so as to vary the reciprocal distance. 13.- Method - in a wrapping machine (2) products (3) in which a wrapper (4) is obtained by wrapping said products (3) repeatedly around it with a continuous strip (5) of wrapping material - for fixing one end (6) of the strip (5) of wrapping material by connecting it to the wrapper (4) at the end of the wrapping, characterized by the fact that it comprises the steps of putting a first elongated element (7), supported by the structure (8) of the machine (2), in an operative condition with respect to the product (3) during wrapping; wrapping of one end (6) of the strip (5) of wrapping material around the elongate element together with the product (3); extension of a section (11) of adhesive tape, transversely to the end (6) of the strip (5) of wrapping material, in contact with the first elongate element (7), so as to make it adhere to the wrapper ( 4); section cut (11) of adhesive tape, fixed to the wrapper (4), thus separating it from a remaining part of the tape supported by a feed coil (10); cutting the strip (5) of wrapping material, fixed to the wrapper (4) and simultaneously held by a clamp (32) so as to create two separate ends, one fixed to the wrapper (4) and the other held by the clamp ( 32). 14. Method according to claim 13, characterized in that it comprises a step of compacting the strip (5) of wrapping material in its arrangement plane (18) transversely to the envelope direction, said compaction stage preceding the step of extending the section (11) of adhesive tape over the wrapper (4). 15. Method according to claim 14, characterized in that it comprises a stage in which a mobile roller (51), inserted between the wrapper (4) already formed on the product (3) and an end (6) of the tape (5) that creates the wrapper (4), is moved with respect to the product (3) so as to vary the distance between the wrapper (4) and said end (6), said roller (51) being moved within a spatial angle (55) delimited by the wrapper (4) and the limb (6) and having a vertex (56) substantially associated with the first elongate element (7), the roller (51) being suitable to be associated with the wrapper (4) or with the limb (6) so as to vary the amplitude of said angle (55).