Apparatus for the application of a thread having a label attached to it to a strip of filter paper in a machine for the automatic production of filter bags for the products to be infused

In an apparatus for the application of a suspension thread of natural fibers having a label attached to it to a strip of filter paper in a machine for the automatic production of filter bags of an infusion product operating in conjunction with a label supply device, the filter paper strip having on one of its surfaces a light coating layer of thermoplastic material, the apparatus comprising means for continuously supplying the strip of filter paper along a working line and, disposed along the latter, folding means for folding the strip of paper into two symmetrical half sections, having the thermoplastic material coated surfaces facing one another along a longitudinal median line, dosing means for supplying discrete quantities of the infusion product at uniform distances to the folded strip, joining means for joining by means of heating the said folded strip transversely between the quantities of infusion product at uniform distances and along the opposite longitudinal edges, and means for cutting the strip at the said transverse joints, and the labels comprising thermoplastic material and being V-shaped, the improvement which comprises:

• a rotary head having radial arms to be disposed downstream of the label supply device, with its front portion behind the strip of filter paper, each radial arm being associated in the plane of rotation of the head with thread-guide means and a series of three nippers, one downstream and two upstream in respect of the direction of rotation of the rotary head;
• means for rotatably actuating the rotary head intermittently;
• means for intermittently halting the filter paper strip in synchronism with intermittent halting of the rotary head;
• means for causing the series of nippers to open and close;
• guide channel means joined in a coplanar manner between the thread-guide means and the nippers of the arms of the rotary head, for communication with the label supply device;
• a first working station comprising means for nipper joining being provided along the guide channel means;
• supply means for supplying a continuous thread to the thread guide means, between the nippers located between the joining means and through the guide channel means;
• first oscillating nipper means for taking, under the action of control means, in uniform succession, single V-shaped labels from the label supply device and to transfer them to the first working station between the nipper joining means, with the continuous thread being between the V-shaped limbs of the labels;
• means for actuating the nipper joining means in order to fix, by means of heating, the labels to the continuous thread, the labels being thereby fixed to the continuous thread and being caused to move, by two of the three nippers, between the thread guide means of each radial arm as a result of the intermittent movement of the rotary head and thus being disposed in the plane of rotation between the said two nippers;
• and
• second and third working stations operating along the path of rotation of the rotary head at one of the radial arms and respectively between two successive radial arms facing the strip of filter paper in the rest position of the rotary head, said second working station comprising cutting means designed to cut the continuous thread downstream of the two nippers, pin means movable perpendicularly to the plane of rotation of the rotary head adapted to intersect, under the action of control means, the plane of the thread externally to the thread at the nipper upstream of the said two nippers, thread tensioning means designed to move the section of thread upstream of the third nipper from its plane, and second oscillating nipper means designed, under the action of control means, to grip the label between the said two nippers and to oscillate with a movement which is opposite to that of the rotary head, thus inserting the said label between the prongs of the said third nipper and winding the thread about the said movable pin means, the third working station comprising suction means extending along the path of the filter paper strip designed, by means of suction across the filter paper strip to cause the thread to adhere to the strip at the area of the label and at least one other point upstream of the label, and joining means of a movable type designed, under the action of control means, to heat the said two areas at which the thread adheres to the filter paper strip, causing localized impregnation of the thread with the thermoplastic material of the coating layer of the strip by diffusion through the filter paper as a result of the heating operation.