Patent Application
20130064612
The present invention relates to a dispenser, particularly but not exclusively to a dispenser for polyethylene.
Traditionally Poly Vinyl Chloride (PVC) has been the preferred polymer for use as cling film. The reason for this being its superior cling properties over Polyethylene (PE). It had been noted however that in certain European countries PVC film was not allowed due to the slight risk of residual monomer and plasticiser migrating to the surface and transferring into the fatty acids in food. PE film has no such problems as it is a pure polymer (no additives) and it is polymerised from ethene gas therefore does not present any migration risks.
Known dispensers would not cut PE as it could not hold the material across the cutting channel in position therefore allowing slippage and the overall channel depth was not sufficient to stretch the material beyond its Elongation @ Break limits (E@B).
Additionally, the applicant has recognised that with known PVC dispensers, and with PE dispensers that are formed from relatively thin plastics, a lack of stability of the hinged lid may compromise the effectiveness of the cut.
To alleviate this problem a new dispenser is described. It comprises the usual features of known film dispensers but the following modifications were made to ensure smooth and effective cutting of Polyethylene film in the extruded body. The modifications were made to overcome greater elongation & break and tear resistance properties of Polyethylene over Poly Vinyl Chloride and to generally improve the cutting action.
According to the present invention there is provided a dispenser for a roll of film material, comprising a cutting arrangement for cutting polyethylene having an upper portion and a lower portion, the upper portion being configured to move in relation to the lower portion between an open position and a cutting position; wherein one of the upper portion and the lower portion comprises a blade, and the other of the lower portion and the upper portion comprises a cutting channel defined by a first pair of legs; and wherein the legs include at least one surface configured to reduce slip of film material across that surface. The upper portion may comprise the blade and the lower portion may comprise the cutting channel.
When the upper portion is in the cutting position, the blade may cut the portion of film material by the time it has been stretched by a ratio of 4:1 from its original length, and/or the blade may extend into the cutting channel by a distance of at least twice the width of the cutting channel. The upper portion may further comprise a second pair of legs, and when the upper portion is in the closed cutting position the second pair of legs may be positioned outside of the first pair of legs. The upper portion may comprise a lid wall, and the dispenser may further comprise a support wall extending between part way down at least one of the second pair of legs and the lid wall.
The cutting stroke was made to be at least double the width of the cutting channel to allow for the stretch of the PE (200%). The width is 6.3 mm therefore the stroke needs to be at least 12.6 mm but more if possible. In order to ensure that the stroke was long enough to extend beyond the E@B of the PE a calculation was devised using Pythagoras Theorem. (In a right angled triangle, the square of the hypotenuse is equal to the square of the other two sides). Therefore taking the cutting legs to form a parallelogram when the blade (which would be central) stretched the film from the blade edge to the cutting leg tips, two right angled triangles would be formed using the stretched film and the cutting leg walls. The leg length would then enable us to determine overall stretch was beyond E@B.
The legs may be parallel to one another. When the upper portion is in the closed cutting position, the blade may be centrally positioned within the cutting channel. The blade may be configured to meet the plane defined by tips of the legs perpendicular to that plane on movement of the upper portion from the open position to the closed cutting position.
The cutting legs were made to be level and blade perpendicular @ point of contact with film then to curve afterwards.
The legs are advantageously at least 1.5 mm thick, to add strength to prevent the whole body collapsing under pressure.
The at least one surface may comprise a thermoplastic elastomer (TPE) coating. Each leg may comprise a top, a front side and a rear side, and the top and front side of each leg and the rear side of one of the legs may be coated with a thermoplastic elastomer coating. The coating may extend down approximately 50% of the front (outer) side of each leg and a portion of the rear (inner) side of one of the legs.
The TPE flexi should be a coating on top of each leg and smeared down 50% of the outside of both sides of the back leg and 50% down the front of the front leg. This was required to hold the film in position across the width of the cutting channel and ensure no slippage occurred which would stop the film being extended enough to allow the cut to take place.
The position of the hinge is moved to improve cutting arc and the inner cutting leg is realigned to sit perpendicular above void (currently adjacent to void).
The angle of the blade should be increased towards 90° to make the blade cut straight down through the film.
The anchor point of the grip assist was to be extended and straightened out slightly to prevent lid catching on this before cutting action has been completed.
There is further provided a dispenser for a roll of film material, comprising a cutting arrangement for cutting polyethylene having an upper portion and a lower portion, the upper portion being configured to move in relation to the lower portion between an open position and a cutting position; wherein one of the upper portion and the lower portion comprises a blade; the other of the lower portion and the upper portion comprises a cutting channel defined by a first pair of legs; the upper portion and the lower portion are hinged together; and wherein the upper portion comprises a void configured to abut the lower portion so as to prevent horizontal movement of the upper portion during movement of the upper portion between the open position and the cutting position. The lower portion may comprise a void configured to abut the upper portion.
The hinge needs to be more robust and either an extra void added or void on lid extended to prevent haul off crushing body and to prevent horizontal movement of lid during cutting action.
The grip assist hinge arm was extended to prevent film to stop film residue from the cut building up in that area.
The blade pips were also modified (more pips per inch and strategically positioned) to ensure a tighter grip in the blade holding channel.
A preferred embodiment of the present invention will now be described with reference to the following figures, in which:
FIG. 1—Shows the extrusion profile of the dispenser (1) with the hinged upper portion (2) in its “open” position.
FIG. 2—Shows a similar arrangement to
FIG. 3—Close-up view of the cutting area of the dispenser, with the upper portion hidden from view (as if it were open).
FIG. 4—Shows a similar arrangement to
FIG. 5—Shows a similar arrangement to
In
The cutting area of the dispenser (1) is shown in
The length of film material would be drawn into the cavity between the legs (6) of the lower portion by the tip of the blade (4) as it passes downwards. As explained before, the co-extruded surfaces prevent slippage of the film material onto the cavity, so as a result the length of film material spanning the legs is being stretched into the V-shape shown.
The stretched portion of film material would be drawn into the V-shape shown, if by this point the blade had not pierced and cut through it. However it has been established that the blade will successfully cut the film material by the time it has been stretched by a ratio of 4:1 from its original length. That is, the depth of the V-shape that is formed by the stretched length of film is twice the original length of the film spanning the legs of the lower portion. Or, in terms of the geometry of the extrusion profile itself, the depth of the channel that the film material is drawn into, is approximately twice its width.
As shown in
The upper portion (2) comprises a support wall (13) (see
The material to be dispensed is presented by a presentation means (16) shown in
The TPE coating inhibits slippage of PE across the cutting channel, allowing the film to be extended enough to allow the cut to take place. The positioning of the TPE coating on top of each leg and smeared down part of the outside of both sides of the legs further inhibits slipping.
The void on the lid inhibits horizontal movement of the lid and increases stability during the cutting action. This helps to ensure that the blade is correctly positioned when it meets the film; i.e. that the blade meets the film at the optimal cutting angle, perpendicular to the film.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1008480.4 | May 2010 | GB | national |
This application is a continuation of PCT Patent Application GB2011/050969 filed on May 23, 2011, which designates the United States, which also claims priority to Great Britain Patent Application No. 1008480.4 filed on May 21, 2010, the entire contents of each of which are hereby incorporated by reference
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/GB2011/050969 | May 2011 | US |
| Child | 13680396 | US |
