Turning – Lathe – Having hollow cutter head
Reexamination Certificate
2001-05-04
2003-01-07
Banks, Derris H. (Department: 3722)
Turning
Lathe
Having hollow cutter head
C082S131000
Reexamination Certificate
active
06502488
ABSTRACT:
This invention relates to apparatus for effecting a cut through a flexible sleeve, such as thin plastics material tubing to form a cut sleeve.
Relatively thin plastics material tubing is used widely in the food processing and other industries for the manufacture of sleeves, either for decorating or labelling a container or for furnishing a container with a tamper-evident device. In the former case, the sleeve is pre-printed with a suitable decorative and informative matter and is then cut to the appropriate length for fitting over the container. Each cut length is then applied to a respective container and secured in position, around the main body of the container. In the latter case, there is no need for the cut length of the sleeve to be decorated in any way and the sleeve does not need to extend over the whole of the container body; it is sufficient for the sleeve to fit over the container closure and the immediately adjacent part of the container body. Such a relatively short sleeve is often referred to as a “band” though for convenience both sleeves and bands will hereinafter be referred to as “sleeves” and sleeving and banding operations as “sleeving”.
A sleeve as described above is usually made of heat-shrink plastics material such as of PVC and, prior to shrinking, typically has a thickness in the region of 40 &mgr;m. Prior to shrinking, the plastics material is highly flexible and also susceptible to static electrical charges. These properties make it relatively difficult to perform the required operations on the sleeve prior to and as the sleeve is fitted on to a container, especially when high-speed sleeving (at rates in excess of 250 containers per minute) is to be performed.
A particular difficulty of a high-speed sleeving machine adapted to fit sleeves on to containers moved through a sleeving station is the cutting of the required length of sleeve for each container, in a highly reliable manner. Various devices have been proposed for high speed cutting of very flexible plastics material tubing used for sleeves, but these tend to be somewhat cumbersome and difficult to install in the relatively confined space of a sleeving machine, unreliable in operation due to their mechanical complexity and also unable to operate at relatively high speeds. Moreover, on account of various out-of-balance components or on having components which must perform reciprocating actions, these prior designs can introduce undesirable vibrations, which in turn can affect the operation of other components associated with the sleeving machine.
It is an aim of the present invention to provide cutting apparatus suitable for use, for example, with a sleeving machine and which apparatus is able to operate consistently and reliably at relatively high cutting speeds, without adversely affecting a sleeving operation, as a whole.
According to one aspect of the present invention, there is provided cutting apparatus for effecting a cut through flexible tubing slidably supported for advancement on a mandrel having a peripheral groove at the location of the intended cut, which apparatus comprises an annulus co-axially surrounding the mandrel, drive means to rotate the annulus about its axis, a blade carrier pivoted on the annulus about an axis parallel to the annulus axis and supporting a cutting blade movable between withdrawn and cutting positions with respect to said groove by pivoting movement of the carrier, the carrier having an armature portion arranged between a pair of electromagnets mounted on the annulus, and current supply means for the electromagnets whereby the armature portion is attracted selectively to either one of the two electromagnets so that the blade may be held in its withdrawn position by one electromagnet until a predetermined length of tubing has been advanced past the groove in the mandrel whereafter the blade may be moved to its cutting position by energisation of the other electromagnet, to effect a cut through the tubing.
It will be appreciated that with the cutting apparatus of this invention, the annulus is rotated continuously and uni-directionally about its axis, and the annulus supports a cutting blade which is movable between a withdrawn position where the blade is clear of the tubing extending axially through the annulus and supported by the mandrel, and a cutting position where the blade is partially received in a groove in the mandrel, so as to cut through the tubing. Compared to the overall mass of the annulus, the cutting blade and its carrier may have a relatively small mass, and by substantially balancing the carrier about its pivotal axis, with a carried blade on one side of the axis and the armature portion of the other side thereof, the overall rotating mass may be balanced for all operating positions, so minimising vibrations and assisting smooth and reliable operation.
It would be possible for the armature to be of a ferromagnetic material and to energise alternately the electromagnets, depending upon the required position of the cutting blade. However, in a preferred form of the invention, the armature comprises a permanent magnet, advantageously of a low mass, high strength rare-earth magnetic material, and which is simultaneously attracted to one electromagnet and repelled by the other electromagnet, upon simultaneous energisation of both electromagnets. In this case, the two electromagnets may be air-cored so that the magnetic armature is not attracted to either electromagnet when not energised, though the electromagnet to which the armature is attracted when the cutting blade is in its withdrawn position may have a small ferrous core, so as thereby to provide a correspondingly small bias to the carrier, to the withdrawn position of the cutting blade.
In order to allow relatively high speed cutting operations to be performed, it is desirable that the carrier is moved rapidly and reliably, at precisely the required moments, between the withdrawn and cutting positions of the cutting blade. To this end, the current supply means may be arranged to provide a high energy pulse to an electromagnet to which the armature is to be attracted, at the moment the carrier is to be moved, whereafter the supply current may fall back to a lower value so as to maintain the armature adjacent the electromagnet to which it was attracted. In a case where the armature has a permanent magnet and the armature is simultaneously attracted and repelled by the two electromagnets respectively, both electromagnets may be provided with high energy pulses better to ensure rapid movement of the carrier between its two positions.
Rapid penetration of the cutting blade through the material of the sleeve to be cut may be assured by having the blade mounted on its carrier in such a way that on contracting the sleeve, friction between the blade and the sleeve moves the blade deeper into the groove in the mandrel. Thus, on the blade being moved towards its cutting position and starting to effect a cut, this frictional drag will assure continued and reliable cutting of the tubing until a sleeve is wholly severed from the tubing.
The apparatus as described above would operate with just one carrier and cutting blade, a sleeve being severed upon the annulus performing a full turn with the cutting blade in its cutting position. In order to increase the rate at which the cutting apparatus may operate, without having corresponding increases in the rotational rate of the annulus, there may be two or more carriers and cutting blades together with associated electromagnets provided on the annulus. In a preferred embodiment of the apparatus, five such assemblies are provided all of which operate simultaneously in the same sense, whereby a sleeve is wholly severed from an uncut length of the tubing upon the annulus performing 72° of arc following initiation of cutting.
The cutting apparatus may be adjustable to suit a wide range of tubing diameters. For each different diameter, an appropriate mandrel must be provided and the bore through the annulus must be sufficient to accommodate that mandrel and t
Andrus Sceales Starke & Sawall LLP
Banks Derris H.
Graham Labelling Systems Limited
Williams Jamila
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