A device and a method for verifying the integrity of product packagings in wrapping machine

Abstract: In a wrapping machine that packages products (15) by enveloping each one in a tubular wrapper (3) with two edges (4a-4b) united lengthwise and heat-sealed thus together, the integrity of the packaging is verified by a device (1) comprising a feeler (8) located at a given point along the wrapping line (2) and offered in sliding contact to the advancing wrapper (3) at an area coinciding with the junction (20) between the edges (4a-4b) and the tubular envelope. The feeler (8) is loaded against a spring delivering a force of known intensity, and able consequently to maintain a stable operating position as long as resistance is offered by the wrappers (3), but will find the gaps in a wrapper of which the edges have failed to unite successfully; the resulting movement of the feeler (8) is sensed by a transducer (9).

Description: The present invention relates to a device by means of which to verify the integrity of packagings fashioned around products in wrapping machines. In particular, the invention relates to a device such as can be utilized with wrapping machines of the type in which packagings are applied to products by feeding the products along a wrapping line and enveloping each one in a wrapper of tubular appearance that exhibits two longitudinal edges, projecting from the tubular portion of the wrapper and extending parallel to the direction of movement, which are united substantially across their full width and secured one to another. Conventionally, such wrappers are fashioned utilizing a continuous film of flexible material decoiled from a roll. Depending on the type of material utilized, the edges of the wrappers can be either heat-sealed one to another or bonded cold by means of a suitable adhesive substance applied initially to at least one of the two edges. In either instance the edges are caused to pass between two rollers, disposed in mutual opposition and rotating convergently with the direction followed by the strip, by which the edges are compressed together. A wrapping method of the type in question is affected by certain drawbacks attributable principally to the fact that the wrapper can become displaced during the formation process from its correct position relative to the enveloped product, in which case the two edges will no longer be correctly united. It is possible as a result that when the two edges are taken up between the rollers, one will appear broader than the other. In practical terms, the narrower edge does not project far enough from the tubular portion of the wrapper to allow a useful breadth of contact with the other edge and thus ensure that both edges will be engaged by the rollers. Consequently, a correct heat-seal or bond is not obtained, and at worst, the finished wrapper will exhibit areas along which the two edges are separated by a longitudinal gap. The object of the present invention is to provide a device applicable to a machine for wrapping products, by which the integrity of packagings can be verified automatically. The stated object is realized in a device according to the present invention for verifying the integrity of packagings fashioned around products in a wrapping machine, typically packagings obtainable from a strip of flexible material advanced in a predetermined feed direction and folded progressively about each one of a succession of products in movement along a wrapping line in such a manner as to form a wrapper of tubular appearance which when closed exhibits a flap disposed parallel to the feed direction and projecting radially from the wrapper, wherein the flap consists in the united longitudinal edges of the strip, characterized in that it comprises feeler means designed to engage the flap in a direction substantially transverse to the feed direction. The present invention relates also to a method by which to verify the integrity of product packagings in wrapping machines, at a given point along a wrapping line. A method according to the invention for verifying the integrity of product packagings in wrapping machines is characterized in that it comprises the steps of: advancing a strip of flexible film material along a wrapping line; folding the film about each one of a succession of products in movement along the wrapping line, in such a way as to fashion a wrapper of tubular appearance with two united longitudinal edges projecting from the tubular portion of the wrapper and sealed or bonded together; subjecting the tubular wrappers at a point near the edges, while in movement along the wrapping line, to a force of intensity such as will encounter opposition in the resistance offered by the wrapper when the two edges are united substantially across their full width and correctly sealed or bonded, and by the same token encounter no opposition in the event that the edges are not completely united and not correctly sealed or bonded. The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which: fig 1 affords a schematic illustration of the device according to the invention associated with a product wrapping line and viewed in plan; figs 2 and 3 are two sectional illustrations of the device taken respectively on A-A and on B-B of fig 1; fig 4 is a further section taken on A-A of fig 1, illustrating a situation in which the tubular wrapper presents a longitudinal gap. Referring to figs 1 and 2 of the drawings, 1 denotes a device, in its entirety, for verifying the integrity of packagings fashioned around products 15, such as can be utilized in a wrapping machine. The packagings are obtained from a continuous strip 16 of flexible material, which is advanced along a feed direction denoted 5 and folded around the successive products 15 as these are in movement along a wrapping line 2 in such a way as to form a wrapper 3 of tubular appearance; in its closed tubular configuration, the wrapper 3 exhibits a flap 4 projecting radially and extending parallel with the feed direction 5, created when the longitudinal edges 4a and 4b of the strip 16 are united one with another. Also indicated in figs 2, 3 and 4 is a conveying table 18 along which the single products 15 are caused to advance, each enveloped in a respective wrapper 3. The two edges 4a and 4b are caused to pass between two rollers 6 from which they emerge compressed and sealed or bonded together. Fig 1 illustrates a portion of the wrapping line 2 comprising the two rollers 6 in question (referred to elsewhere in the specification as "heat-seal rollers" for the sake of simplicity), which are rotatable about mutually parallel vertical axes. In the example of the drawings, the edges 4a and 4b of the strip are shown as projecting from the underside of the tubular portion 3a presented by the wrapper 3. In order to illustrate the already united edges 4a and 4b in fig 1, accordingly, the stretch of the wrapping line 2 extending beyond the heat-seal rollers 6 in the feed direction 5 is depicted omitting both the tubular wrapper 3 and the enveloped product 15. In this way it becomes possible both to show the two edges 4a and 4b and to indicate the junction, denoted 20, between the edges and the tubular portion 3a of the wrapper 3. The wrapping line 2 also comprises two frusto-conical bending rollers 7, rotatable about vertical axes and with mating profiles, between which the edges 4a and 4b are caused to pass once heat-sealed. The function of these rollers 7 is to bend the two edges 4a and 4b initially toward the tubular portion 3a. With reference in particular to fig 2, the device 1 to which the invention relates comprises a frame 10, and articulated to the frame, a pair of mutually parallel arms 13 and 14 interconnected by a rod 11 in such a way as to form a quadrilateral linkage 19 occupying a plane normal to the feed direction 5 of the conveying line 2. The device further comprises feeler means, carried by a free end of the rod 11, of which the actual feeler element 8 appears as a flat horizontal leaf disposed substantially parallel with and riding against the underside of a tubular portion 3a advancing along the wrapping line 2, also tension means 12, represented in fig 2 as a spring 12 of which the two opposite ends are anchored respectively to the frame 10 and to the rod 11; the function of the spring is to subject the rod, hence the feeler 8, to a force of given intensity and direction such as will maintain a stable operating position whereby the feeler 8 stays in sliding contact with the wrappers 3 moving along the wrapping line 2. The force in question, and the relative direction, are indicated by the arrow denoted F in figs 1, 2 and 4. The feeler 8 terminates in a rounded tip 8a (fig 1) positioned to interact with the wrappers 3, as will be described more fully in due course. The tip 8a of the feeler 8 is designed to enter into contact with the wrapper 3 preferably at the area of the junction 20 between the edges 4a and 4b and the relative tubular portion 3a. The area across which the edges 4a and 4b are effectively heat-sealed, given a correctly made join, commences immediately beyond the junction 20 in the radial direction. The device 1 according to the invention is shown in fig 1 (continuous lines) operating beyond the bending rollers 7 in the feed direction, from a position to one side of the edges 4a and 4b and facing the edge denoted 4a. In the example illustrated, the tip 8a of the feeler 8 engages in contact with the area of the junction 20 on the inside of the angle formed by the two edges 4a and 4b when bent toward the underside of the tubular portion 3a of the wrapper 3. The option also exists, alternatively or additionally, of locating the device 1 at a given point between the heat-seal rollers 6 and the bending rollers 7. This solution is illustrated likewise in fig 1, which shows the device (phantom lines) positioned on the opposite side, facing the edge denoted 4b. In this instance the feeler 8 will engage the area of the junction 20 by entering into contact with the corresponding edge 4b, and more exactly with the angle formed between the edge 4b and the tubular portion 3a of the wrapper 3, at a point along the wrapping line 2 where the two edges 4a and 4b have not yet been bent and are thus disposed substantially perpendicular to the tubular portion 3a. In each case, the resultant generated by the spring 12 and the parallelogram through the feeler 8 is applied in a direction F substantially transverse to the feed direction 5 followed by the wrappers 3. 9 denotes a proximity transducer associated with one member of the quadrilateral linkage 19, for example the rod 11, and capable of detecting any movement of the feeler 8 away from its stable operating position. Immediately beyond the device 1, following the feed direction 5, is a fixed folding element 17 typically affording an inclined plane angled in such a way as to induce a further bending action by which the edges 4a and 4b of the wrapper 3 are substantially flattened against the underside of the tubular portion 3a. In operation, as long as the wrappers 3 continue to advance with their two longitudinal edges 4a and 4b correctly united and heat-sealed, the feeler 8 remains in a condition substantially of static equilibrium, which for the purposes of verifying the integrity of the wrapper 3 will correspond to the stable operating position aforementioned, i.e. a position maintained when the action of the spring 12 is opposed by the reaction of the wrapper 3 registering at the area of the junction 20. In this situation, illustrated in figs 1 and 2, the feeler 8 remains substantially motionless by virtue of the fact that when correctly united and heat-sealed, the advancing edges 4a and 4b continue to hold their positions relative to one another when passing through the device 1, signifying that there are no breaks in continuity along the area of the junction 20 such as would diminish the reaction offered by the wrapper 3 to the action of the spring 12 applied through the feeler 8. Conversely, fig 4 shows a situation in which the two longitudinal edges 4a and 4b of the advancing wrapper 3 are unequally proportioned. In the example illustrated, the edge denoted 4b is broader than that denoted 4a. Thus, with one edge 4a failing to project from the tubular portion 3a of the wrapper 3, there is no available width that can be utilized to fashion a lapped join with the remaining edge 4b. The feeler 8 is illustrated in fig 4 displaced from its position of static equilibrium by the force of the spring 12, as a result of the edges 4a and 4b having failed to unite and consequently been unable to offer any resistance, or at least able to offer insufficient resistance, to the action of the spring 12. The upshot in any event is that the feeler 8 will find the gap left between the two longitudinal edges 4a and 4b and slip between the product 15 and the tubular portion 3a of the wrapper 3. In other words, the spring 12 is capable of generating a force P, applied through the feeler 8, such as will be opposed by the resistance the wrapper 3 is able to offer when the edges 4a and 4b are correctly united and heat-sealed; equally, in the event that any of the wrappers 3 should present longitudinal gaps 21, the same force P will also be sufficient to push the feeler 8 into the gaps 21. The proximity transducer 9 is set up in such a way as to generate a signal when the rod 11 and the feeler 8 are displaced from the aforementioned condition of equilibrium. The device 1 further comprises means of conventional embodiment, illustrated simply as a block denoted 22 in the drawings, capable of receiving the signal from the proximity transducer 9, identifying any wrapper 3 with incorrectly united longitudinal edges 4a and 4b and thereupon triggering its rejection. Such means 22 might also be capable of piloting the wrapping machine to shut off automatically, so that the operator can remove substandard packagings and remedy the cause of the trouble.

Claims: A device for verifying the integrity of packagings fashioned around products in a wrapping machine, typically packagings obtainable from a strip (16) of flexible material advanced in a predetermined feed direction (5) and folded progressively about each one of a succession of products (15) in movement along a wrapping line (2) in such a manner as to form a wrapper (3) of tubular appearance which when closed exhibits a flap (4) disposed parallel to the feed direction and projecting radially from the wrapper, wherein the flap consists in the united longitudinal edges (4a, 4b) of the strip (16), characterized in that it comprises feeler means (8) designed to engage the flap (4) in a direction substantially transverse to the feed direction (5). A device as in claim 1, wherein the feeler means (8) are disposed in such a manner as to interact with an area corresponding to the junction (20) between the edges (4a, 4b) and a tubular portion (3a) of each wrapper (3). A device as in claim 1 or claim 2, further comprising tension means (12) such as will displace the feeler means (8) in the transverse direction with a force (P) of predetermined intensity. A device as in preceding claims, wherein the position of the feeler means (8) is monitored with the aid of sensing means (9) able to detect a displacement of the feeler means (8) in the transverse direction, allowed when the unsuccessfully united edges (4a, 4b) of the wrapper (3) are separated by a longitudinal gap (21), and thereupon relay an output signal to control means (22) such as will identify and indicate the defective wrapper (3). A device as in preceding claims, further comprising a quadrilateral linkage (19) mounted to a frame (10), composed of two arms (13, 14) pivotably associated with the frame (10) and interconnected by a rod (11) carrying a feeler element (8) of the feeler means, wherein the tension means (12) operate between the frame (10) and the rod (11) in such a way as to apply the force (P) of predetermined intensity to the feeler element (8). A device as in claim 4, wherein sensing means (9) consist in a proximity transducer associated and operating in conjunction with one member of the quadrilateral linkage (19). A device as in preceding claims, wherein the tension means (12) consist in a spring (12). A device as in preceding claims, wherein the feeler element (8) consists in a flat horizontally disposed leaf terminating in a rounded tip (8a) positioned to interact with the wrappers (3). A method for verifying the integrity of product packagings in wrapping machines, characterized in that it comprises the steps of: advancing a strip (16) of flexible film material along a wrapping line (2); folding the film about each one of a succession of products (15) in movement along the wrapping line (3), in such a way as to fashion a wrapper (3) of tubular appearance with two united longitudinal edges (4a, 4b) projecting from the tubular portion (3a) of the wrapper (3) and sealed or bonded together; subjecting the tubular wrappers (3) at a point near the edges (4a, 4b), and while in movement along the wrapping line (2), to a force (P) of intensity such as will encounter opposition in the resistance offered by the wrapper (3) when the two edges (4a, 4b) are united substantially across their full width and correctly sealed or bonded, and by the same token will encounter no opposition in the event that the two edges (4a, 4b) are not completely united and not correctly sealed or bonded. A method as in claim 9, wherein the force (P) is applied through the agency of tension means (12) acting on a feeler element (8) disposed in contact with an area of the wrapper (3) corresponding to the junction (20) between the two edges (4a, 4b) and the tubular portion (3a) and capable of movement between a substantially static position, maintained as a result of the resistance offered by a wrapper (3) when the two edges (4a, 4b) are united substantially across their full width and correctly sealed or bonded, and an extended position, assumed in the event of wrappers exhibiting longitudinal gaps (21) as a result of the edges (4a, 4b) having failed to unite and to seal or bond correctly, in which the feeler element (8) finds the gap (21). A method as in claim 9 or 10, wherein the extended position of the feeler element (8) is sensed by means of a transducer (9), of which the output signal is relayed to control means (22) such as will respond to the extending movement of the feeler element (8) by identifying and indicating the wrappers (3) exhibiting longitudinal gaps (21).

Inventors: SPATAFORA MARIO, SPATAFORA, MARIO
Applicants: AZIONARIA COSTRUZIONI ACMA SPA, AZIONARIA COSTRUZIONI MACCHINE AUTOMATICHE-A.C.M.A.-S.P.A.
Application year: 1996
Main classification: B65B57
IPC codes: B65B57