Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – With cutting – punching – piercing – severing – or tearing
Reexamination Certificate
1999-07-26
2003-01-14
Gray, Linda (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
With cutting, punching, piercing, severing, or tearing
C156S251000, C156S308400, C156S530000, C053S451000, C053S551000, C053S552000, C053S479000, C053S480000
Reexamination Certificate
active
06505664
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to rotary mechanisms for cutting and/or sealing web materials. It is particularly concerned with the cutting and/or sealing of a continuously moving web by apparatus comprising counter-rotating rotors between which the web passes.
Heat sealing operations in such apparatus relies on the web material being momentarily engaged between opposed faces of the rotors as those faces come into juxtaposition and apply heat and pressure to the web material. If the material is not also to be severed by the heat and pressure, the contact pressure can be critical. To safeguard against inadvertent severing of the material it can be arranged that the mutually opposed faces are held apart at a small spacing as they come together. For this purpose it is known to provide contacting bearer elements standing slightly proud of the sealing faces on the rotors adjacent the web-gripping faces, as described in WO95/01907 (U.S. Pat. No. 5,548,947), that maintain a gap between those faces. For high speed running, these bearer elements can extend circumferentially in front of the sealing faces in the direction of rotation, to help ensure that dynamic disturbances from their initial contact do not affect the sealing process adversely.
For sealing web materials such as thermoplastic-coated paper, it is known to apply a crimp to seal the material more securely. Thus, the rotor sealing faces are formed with complementary arrays of V-grooves, running in the circumferential direction over the faces. If the complementary arrays are not closely aligned, however, a non-uniform spacing appears with an increased gap on one face of each V-groove and a reduced gap on the opposite face. This asymmetry produces a resultant lateral force component tending to limit such misalignment, but the higher pressure where the gap is reduced can damage the web material.
If the V-groove arrays are extended over the bearer elements, they will tend to correct any misalignment as they come into engagement, before the sealing faces engage the web material. However, as the faces of the bearer elements make direct contact, there are then very high local peak pressures experienced which can give rapid wear. Such wear may occur because there may be a relative misalignment between the pairs of bearer faces at opposite axial ends of a sealing face, since even a very small dimensional difference will prevent the grooves of both pairs of bearer faces meshing fully. Close control of dimensional tolerances can ensure that misalignment from this source will not adversely affect the web material, but larger misalignments can be created by disturbing forces, such as differential thermal expansion effects. In that case, because the misalignment will only be reduced to the extent that the disturbing forces are balanced by the resultant lateral force on the bearer element grooves, their meshing may still leave significant non-uniformity in the spacing between the crimping grooves on the sealing faces.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a rotary mechanism comprising at least one pair of rotors mounted for counter-rotation on parallel axes each having radially projecting arms with cutting and/or sealing means on radially outer faces of the arms to cut and/or seal web material between juxtaposed outer faces of the arms of said pair of rotors, the arms being provided with bearer elements arranged to contact each other when the faces are brought together and set a spacing between said juxtaposed faces, the cutting and/or sealing means of each outer face being located between first and second said bearer elements of the respective rotor arm, the cooperating first bearer elements at one end of the juxtaposed faces comprising means locating the arms relative to each other in the direction of the axes of rotation of the pair of rotors, and the cooperating second bearer elements at the other end of said faces permitting relative movement in said axial direction.
In this way it is possible firstly to reduce wear through relative misalignment between the bearer elements at opposite ends of a pair of sealing faces because the second pair of bearer elements are not constrained laterally by their engagement. In addition, however, it allows the adoption, in a preferred form of the invention, of an arrangement in which each said cooperating pair of first elements have on each element a pair of locating faces extending in substantially radial planes, said faces of one element of the pair being engaged between said faces of the other element of the pair.
While disposing said pairs of faces precisely in radial planes provides a form of engagement that positively precludes lateral misalignment, in practice the same effect can be achieved if they are inclined to some degree from the true radial direction.
Preferably, said pairs of faces are formed as mating male and female elements occupying only a minor part of the width of their bearer faces, the remaining parts of which will provide radial location setting the spacing between the rotor arms. In that case, said male and female elements may have respective radially outer and inner faces which are maintained out of contact with each other.
For effective use of the bearer elements to locate the arms of the respective rotors relative to each other, it is convenient to arrange that one rotor of the pair is resliently biased towards the other.
According to another aspect of the invention, there is provided a rotary mechanism comprising a pair of rotors mounted on respective carriers for counter-rotation on parallel axes and each rotor having radially outer faces provided with cutting and/or sealing means to cut and/or seal web material engaged between said outer faces, one of the carriers being displaceably supported and being acted upon by biasing means to urge said outer faces into engagement, means being provided to limit the displacement of said one carrier by said biasing means, said biasing means being arranged to bear on said one carrier at a location substantially coincident with a plane containing the axes of the two rotors, and the displacement limiting means being provided by at least one stop element also substantially coincident with said plane of the rotor axes.
Such a mechanism can include with advantage the locating bearer elements of the first aspect of the invention so that transverse seals are made at intervals across a continuous tubular web and the web is severed simultaneously in the width of the seals in order to form a series of individual sealed packets.
If a rotary mechanism according to the first aspect of the invention is provided with web cutting means, the arrangement of the bearer elements is also able to offer an advantage as compared with the bearer elements referred to about complementary crimping V-grooves. As has already been explained, in the prior art rotors with grooved bearer elements, the V-grooves cannot be relied on to eliminate transverse misalignment in the mechanism and such misalignment will also cause a radial displacement when the bearer element faces engage each other. By the use of the bearer elements of the present invention, any correction of misalignment does not affect the relative radial positions of the rotor arms, so cooperating cutting elements on the juxtaposed outer faces of the arms remain unaffected.
This is particularly useful if the cutting elements are intended for crush cutting of the web material. In this cutting technique, the material is severed when it is nipped between a sharp-edged cutter element and an anvil element. The action requires a precise setting of the two elements relative to each other to ensure on the one hand that the cutting action is complete and on the other hand that the working life of the elements is not impaired by excess pressure loads.
It is usual to provide means for adjusting crush cutting elements in the radial direction to set them precisely and this is a requirement that can occur independently of the need to ensure t
Blundell Brian Francis
Cahill Michael John
Fincham Kevin Richard
Franklin Paul
Vernon Geoffrey William
Gray Linda
Lipton, a division of Conopco, Inc.
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