This invention relates particularly to roll-fed labelling apparatus as may be used for applying labels taken from a label web to a variety of articles. Such articles are often containers found in production, packaging and bottling of drinks, foods, household products, toiletries, oils, paints and the like and manufacture of plastic, glass, metal and other containers.
In conventional roll-fed labelling apparatus a label web is taken from a label roll stand and delivered via label feed and tensioning apparatus to a cutter drum. In order to maintain the tension in the label web, the cutter drum rotates at a faster velocity at its circumference than the supplied web, requiring an immediate acceleration of the web. In practice, unless there is an appropriate degree of slippage of the label on the drum, the label will stretch undesirably or even tear. However, the requirement of catering for such slippage is itself problematic, imposing demanding specifications on the coefficients of friction of the drum surface, and in respect of the registration and glue application processes. Typically, after the web is cut into individual labels, the labels are passed on to an adjacent vacuum drum. The vacuum drum also rotates at a faster velocity than the cutter drum, and thus the aforementioned requirements relating to slippage also apply at this stage.
The labels may then be coated on their back face with an adhesive, typically at their leading and trailing edges and then passed from the vacuum drum to respective containers or articles brought into juxtaposition with the label on the vacuum drum by a turret or other conveyor.
The apparatus for applying the adhesive to the label generally includes a further wheel or roller having a knurled or shaped surface and glue wires which are positioned to prevent labels from dislodging from the vacuum drum and falling into the gluing apparatus or other equipment, causing breakage, inefficiencies and down time. These glue wires, however, have been found to be unreliable themselves, breaking from time to time and giving rise to the above problems.
Thus it may be seen that labelling machines conventionally have used a series of rotating drums for the transport of labels through a series of stages. The labels are transferred from the surface of one drum to the surface of the next drum, and the labels are generally held on the surface of the drum by a vacuum.
The relative speeds of the drums are critical and even a slight error in the speed of one of the drums can lead to substantial problems or inefficiencies. Such errors may be hard to avoid in view of unpredictable and inconsistent levels of slippage and label stretch, causing labels to be wrinkled or creased as they are transferred from one drum to the next.
An object of the present invention is to reduce the risk of such wrinkling or creasing by simplifying the process required to register and cut the label web, and thereafter apply adhesive to the labels. In one aspect, the invention enables this by enabling more of these processes to be undertaken while the label is on a single drum, thereby also reducing the requirement of transferring labels from one drum to another.
U.S. Pat. No. 4,632,721 Hoffmann goes some way in attempting to meet the aforementioned objective. Hoffman teaches the use of a knife carried directly on a vacuum drum in an attempt to negate the requirement of a separate cutter drum. However, Hoffman teaches the need for an interaction between the vacuum drum and stationary blades which together sever or shear each label from a continuous web. Glue applying rollers are also positioned in close proximity to the vacuum drum. However, a disadvantage of the art taught by Hoffmann is that it the gripping pads, which act to hold the label to the vacuum transport drum, requires to retract and protrude at appropriate and exact times during the rotation of the drum in order to avoid interference with the stationary blades in one case and to cause the label to press against the glue rollers in another case. Thus, Hoffmann does not entirely overcome the need to provide for precise relative speeds of one mechanism in relation to another. It is also noted in the present invention that the act of shearing or severing label web between a moving blade and a stationary blade is not entirely satisfactory. Thus, an object of the present invention is to mitigate these disadvantages in the art.
Further objects of the present invention will become apparent from the following statements and description.
According to a first aspect of the present invention there is provided a roll-fed labelling apparatus comprising delivery means for delivering a label web to a rotary cutting drum, and one or more [separating] cutting means associated with the cutting drum for [separating, parting, severing or] cutting the label web into individual labels while held by a relative negative pressure on the circumferential surface of the drum, the apparatus being associated with a container delivery means whereby containers are delivered into juxtaposition with separated labels located on the rotary cutting drum to enable transfer of the said separated labels to respective containers.
Preferably the [separating] cutting means are provided on or near the circumferential surface of the drum.
Preferably the [separating] cutting means comprises a sharp edged or pointed device or instrument. The [separating] cutting means may be a [cutting] blade. Alternatively said [separating] cutting means may be a heated device or appliance, a water, ultrasonic or laser cutting device, or any device for [perforating and tearing] cutting the web into individual labels.
[While] Where there are a plurality of cutting blades, at each blade there may be provided a slot in the cuter circumferential surface of the rotary cutting down and preferably at least part of the cutting edge of each blade protrudes through the slot allowing contact of the blade with the label web on the cutting drum. The blade may be connected to a piston located within a cylinder wherein movement of the piston and blade is provided by a relative change in air pressure across the piston. Preferably, the means for providing a relative negative pressure at the outer circumferential surface of the rotary cutting drum is also used, when required, to provide the relative pressure change across the piston in the cylinder. Other devices such as mechanical, electro-mechanical, pneumatic or hydraulic devices may be used in place of the piston.
According to a second aspect of the present invention the aforesaid delivery means is such that the label web is delivered to the rotary cutting drum under a low or negligible tension. The delivery means may comprise a free loop mechanism for this purpose.
An advantage of this is that minimal, negligible or even zero slippage may occur in respect of the label web or individual labels on the rotary cutting drum. Furthermore, as the label web is supplied at a relatively low or negligible tension, the label web is not caused to stretch or tear and materials of low tensile strength may be used.
According to a third aspect of the present invention the roll-fed labelling apparatus further comprises an adhesive applicator provided in close proximity to the rotary cutting drum to enable labels to receive adhesive prior to their transfer to their respective containers. Preferably the adhesive applicator comprises means for spraying adhesive onto the back faces of the labels. Preferably, the adhesives applicator has means for pulsing the spray such that the adhesive is ejected onto the leading and trailing edges of the labels.
Alternatively, the adhesive applicator may be arranged to spray the adhesive in a pattern such that the leading and trailing edges of adjacent labels are applied with adhesive in a single action. The rotary cutting drum may be provided with an angular profile at each slot and the adhesive applicator may also be positioned at an angle to the radius of the cutting drum so that contamination of the slot during supply of the adhesive may be reduced or minimised.