GB2204301A

GB2204301A - Magazine for plastics bag stacks

Info

Publication number: GB2204301A
Application number: GB08709785A
Authority: GB
Inventors: Keith Stott
Original assignee: NAUTILUS MODELS Ltd
Current assignee: NAUTILUS MODELS Ltd
Priority date: 1987-04-24
Filing date: 1987-04-24
Publication date: 1988-11-09
Also published as: GB8709785D0

Abstract

A magazine for a printing apparatus, especially a hot foil printing apparatus for the application of a design to plastics bags, has a base which moves vertically between a lower "full" position and an upper "empty" position, the profile of the base being variable between arcuate at the lower position and flat at the upper position, whereby the topmost bag in a stack thereof, the stack having a greater cumulative edge thickness than central thickness and being carried by the magazine floor, always presents a flat surface. <IMAGE>

Description

MAGAZINE FOR PRINTING APPARATUS This invention relates to printing apparatus, for example hot foil printing apparatus for the application of a design to a bag made from a plastics material, and in particular provides a magazine for use therewith.

Bags made from plastics materials, for example polyethylene, are commonly used for the packaging of consumer goods, especially of perishable commodities such as food products and in particular for frozen food and frozen food products. The bags are generally formed with a fold at the bottom end of the bag, the back and front faces being welded together along their side edges. Before being charged with goods, such bags generally have a design printed on one or both faces, the design indicating a trade mark or name denoting the origin of the goods, an indication as to the nature, character or quality of the goods, or the quantity, price, shelf life and so on.Such designs are generally applied by the process of hot foil printing, in which a stack of bags is contained in a magazine and individual bags are removed from the top of the stack by a vacuum pick-up head and moved to a printing station.

It is a disadvantage of existing printing machines, when used with a stack of bags of the type described, that the cumulative thickness of the side seams of the bags causes the bags at the upper end of the stack to assume a concave arcuate form, with the result that the vacuum pick-up head is unreliable in opertion, since it is not presented with a flat surface.

It is an object of the present invention to overcome this disadvantage.

According to the invention, we provide a magazine for a printing apparatus, in which the floor of the magazine has a profile which is variable between substantially flat and arcuate.

When the magazine contains a stack of bags, the profile of the magazine floor, or degree of curvature thereof, is arranged such that the difference in height between the edges of the floor and the apex of the arc is essentially equivalent to the difference between the cumulative height of the bags at their central regions and at their welded edge regions respectively, thereby causing the topmost bag in the stack to present a substantially flat surface. As the bags are picked off the top of the stack and the stack diminishes in height, the profile of the magazine floor is arranged to render it less arcuate to reflect the lessened cumulative height difference between the central and edge regions of the bags. Preferably the variation in curvature is automatic, depending on the loading of bags in the magazine.

In a preferred aspect, the magazine is of the type in which the floor thereof is movable vertically between a lower "full" and an upper "empty" position, upward movement being automatic to maintain the position of the topmost bag substantially constant, and the degree of curvature of the magazine floor is dependent upon the vertical position thereof.

In one embodiment, in a magazine floor assembly, the magazine floor is formed from bendable, preferably resilient, material and the outer side edges thereof are carried for vertical movement of the floor in frame members, the frame members converging downwardly, whereby the distance between the said outer side edges is smaller when the magazine floor is at or towards the lower end of the frame members compared with the distance when the floor is at or towards the upper end of the frame members, the floor thereby having a curvature the degree of which varies in dependence upon the vertical position of the floor with respect to the frame members.

Preferably, the distance between the frame members at the upper ends thereof is such that the magazine floor is substantially flat, the degree of curvature being minimal or substantially zero, when the magazine is at the upper "empty" position.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 is a side elevation of a magazine floor assembly according to the invention, and Figure 2 is an end elevation of the magazine floor assembly of Figure 1.

Referring fristly to Figure 1, which shows only the main elements of a magazine floor assembly according to the invention for the sake of clarity, an arcuately-profiled magazine floor 11 formed from a sheet of resilient acrylonitrile-butadiene-styrene polymeric material is supported at its corners by lugs 12. Each lug carries an axle 13 on which is journalled a pair of rollers 14, 15, one on each side of the lug (see Figure 2). The outer rollers 14 run against the inside edges of frame members 16 (shown dashed in Figure 2 for clarity) which converge downwardly and diverge upwardly and are joined by upper and lower cross-pieces 17 and 18. The rollers 14 are biased into contact with the frame members 16 by the resilience of the floor 11.

As shown in Figure 2, the magazine floor assembly also includes frame members 19 which are raisable and lowerable by conventional means (not shown) housed in the right-hand end framework 20, to maintain the topmost bag in the stack at a constant height or for re-loading with a fresh supply of bags, as the case may be. The frame members 19 support a flat sheet member 20 which carries inverted L-shaped members 21. The inner rollers 15 are engaged loosely in the slot between the underside edges of the L-shaped members 21 and the upper surface of the sheet member 20.

In use, the frame members 19 are moved upwardly, to accommodate the diminishing height of a stack of bags (not shown) on the magazine floor 11, or downwardly, for re-loading the magazine with a fresh supply of bags, and this movement is transmitted to the floor of the magazine by means of the rollers 15 and the lugs 12. On downward movement, as shown in Figure 2 with the rollers 15 in contact with the L-shaped members 21, the converging frame members 16 constrain the rollers 14 to move together, thereby forcing a greater degree of curvature in the arcuate floor 11. Conversely, on upward movement of the frame members 19, the resilience of the floor 11 moves the rollers 14 further apart, to the extent permitted by the upwardly-diverging frame members 16, until the degree of curvature of the arcuate floor is substantially zero, as indicated in dashed outline at 22 in Figure 2.

Although a magazine assembly as described above is particularly intended for use with a hot foil printing apparatus, similar magazines may in fact be employed in any other application in which the cumulative height of a stack of substrate articles is different at the centre thereof compared with the edge regions thereof.

Claims

1. A magazine for a printing apparatus, in which the floor of the magazine has a profile which is variable between substantially flat and arcuate.

2. A magazine according to Claim 1, in which the printing apparatus is for printing on bags or other substrate articles which in a stack thereof have a cumulative edge thickness greater than the cumulative central region thickness, the difference in height between the edges of the magazine floor and the apex of the arcuate profile being essentially equivalent to the difference between the cumulative edge thickness and central region thickness of the articles in the magazine, whereby the topmost article in the stack presents a substantially flat surface.

3. A magazine according to Claim 1 or Claim 2, in which the floor of the magazine is movable vertically between a lower "full" and an upper "empty" position, upward movement being automatically controlled to maintain the position of the topmost bag substantially constant, the degree of curvature of the magazine floor being dependent upon the vertical position thereof between the extremes.

4. A magazine according to any preceding claim, in which the magazine floor is formed from bendable material and the outer side edges thereof are carried for vertical movement of the floor in frame members which converge downwardly, whereby the distance between the said outer side edges is smaller when the magazine floor is at or towards the lower ends of the frame members compared with the said distance when the floor is at or towards the upper ends of the frame members, the floor thereby assuming a curvature which varies in dependence upon the vertical position of the floor with respect to the frame members.

5. A magazine according to Claim 4, in which the magazine floor is formed from bendable resilient material, whereby the curvature assumed by the floor remains substantially constant between the edges thereof at any given position of the floor with respect to the frame members.

6. A magazine according to Claim 4 or Claim 5, in which the distance between the frame members at the upper ends thereof is such that the magazine floor is substantially flat, the degree of curvature being minimal or substantially zero, when the magazine is at the upper "empty" position.

7. A magazine according to any preceding claim, in which the printing apparatus comprises a hot foil printing apparatus for the application of a design to bags made from a plastics material.

8. A magazine for a printing apparatus, substantially as described with reference to and as illustrated in the accompanying drawings.