Device and method for verifying the integrity of product packaging in a wrapping machine

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

BACKGROUND OF THE INVENTION 
The present invention relates to a device by means of which to verify the 
integrity of packaging fashioned around each of a succession of products 
which are being packaged by a wrapping machine. 
In particular, the invention relates to a device such as can be utilized 
with wrapping machines of the type in which packaging is applied to 
products by feeding the products along a wrapping line and enveloping each 
one in a tubular wrapper which has two longitudinal edges, projecting from 
the tubular portion of the wrapper and extending parallel to the direction 
of movement, which edges, if all goes well, are each 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 be 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 have areas along which 
the two edges are separated by a longitudinal gap. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a device applicable to a 
machine for wrapping products, by which the integrity of packaging can be 
verified automatically. 
The stated object is realized in a device according to the present 
invention for verifying the integrity of packaging fashioned around 
products in a wrapping machine, typically packaging 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 has a flap disposed parallel to the 
feed direction and projecting radially from the wrapper, wherein the flap 
is made of the united longitudinal edges of the strip and is engaged by 
feeler means operating in a direction substantially transverse to the feed 
direction. 
The invention relates also to a method by which to verify the integrity of 
product packaging in a wrapping machine, at a given point along a wrapping 
line. A method according to the invention for verifying the integrity of 
product packaging in a wrapping machine 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, so as to fashion a wrapper of tubular appearance with two united 
longitudinal edges projecting from the tubular portion of the wrapper and 
(if all has gone well) sealed or bonded together, and thereafter, 
subjecting the advancing wrapper at a point near the edges 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. By the same token, no opposition 
will be encountered in the event that the edges are not completely united 
and thus are not correctly sealed or bonded.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 1 and 2 of the drawings, the numeral 1 denotes a device, 
in its entirety, for verifying the integrity of packaging 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 has a flap 
4 projecting outwardly from the tubular portion and extending parallel 
with the feed direction 5. The flap 4 is created when the longitudinal 
edge margins 4a and 4b of the strip, beyond the tubular portion of the 
wrapper 16, are united confrontingly facewise 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, or in a respective segment of the wrapper 3, unless and until 
the packaging strip stock is cut into individual pieces, whether before or 
after the strip stock is wrapped about the products. 
The two edge margins 4a and 4b are caused to pass between two rollers 6 
from which they emerge compressed and sealed or bonded together 
confronting face to confronting face. 
FIG. 1 illustrates a portion of the wrapping line 2 comprising two rollers 
6 (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 shown in the drawings, the edge margins 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 edge 
margins 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 edge margins 4a and 
4b and to indicate the junction, denoted 20, between the edge margins and 
the tubular portion 3a of the wrapper 3. The wrapping line 2 also 
comprises two frusto-conical bending rollers 7, which are rotatable about 
vertical axes and with mating profiles, between which the edge margins 4a 
and 4b are caused to pass, once they have been subjected to the 
heat-sealing step. The function of these rollers 7 is to bend the two edge 
margins 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 1 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, and therefore 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 (or wrapper segments) 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 a wrapper 3 preferably at the area of the junction 20 
between the edge 4a and 4b and the tubular portion 3a. The area across 
which the edge margins 4a and 4b are effectively heat-sealed, given a 
correctly made join, commences immediately beyond the junction 20 in the 
outward 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 edge margins 4a and 4b and facing the edge 
margin 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 edge margins 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 (shown in phantom lines) positioned on the opposite side, 
facing the edge margin denoted 4b. In this instance, the feeler 8 will 
engage the area of the junction 20 by entering into contact with the 
corresponding edge margin 4b, and more exactly with the angle formed 
between the edge margins 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. 
The numeral 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 providing an inclined plane angled 
in such a way as to induce a further bending action by which the edge 
margins 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 edge margins 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 edge margins 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 edge margins 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 margin 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 joint with the remaining edge margin 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 edge margins 
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 edge margins 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 edge margins 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.