FROM A STACK

The present invention relates to apparatus and a method for removing articles from a stack, and is concerned particularly, although not exclusively, with apparatus and a method for removing delicate or friable articles, such as biscuits, from a stack.

When manufacturing biscuits it is often necessary to transfer the biscuits from a substantially vertical stack to a substantially horizontal conveyor. This operation is commonly known as de-stacking. When automating a de- stacking operation in the production of biscuits or similarly delicate articles, care must be taken when designing the handling devices to ensure that the biscuits are not damaged. Typically, damage may be caused due to the rapid stop-start of the biscuits within the stack as they are moved downwards during the de-stacking process. At high operational speed this manifests itself as a vertical vibration of the stack. This is particularly noticeable in equipment suitable for high volume production of biscuits and commonly results in a crumbling or cracking of the biscuits.

One known prior art device which attempts to address this problem is described in U.K. Patent No 2 216 508. This device uses a toothed wheel to remove, one at a time, articles from the bottom of a stack. However, the vertical downward movement of the stack is not at a constant speed and therefore vibration of the stack is not eliminated.

According to a first aspect of the present invention there is provided apparatus for removing articles from a

stack, the apparatus comprising conveying means arranged, in use, to be located substantially below a stack of articles in a stack retaining means, and a number of projections located on the conveying means, the projections being arranged in use to remove successively the lower most article in the stack as the conveying means moves beneath the stack, wherein a portion of the conveying means is arranged, in use, to convey a lower most article in the stack downwardly with respect to the stack retaining means at least until the lower most article is conveyed beyond a horizontal extent of the stack.

Preferably, the arrangement is such that, in use, the stack of articles maintains a downward motion with respect to the stack retaining means. Preferably, in use, the downward motion of the stack is substantially continuous.

Preferably, the conveying means comprises an endless belt or track, which may be driven by a pulley.

Preferably, the portion of the conveying means directly below the stack is arranged, in use, to travel downwardly with respect to the stack in the direction of travel of the conveying means.

Said portion of the conveying means is preferably substantially flat.

The angle between the said portion *sf the conveying means and the horizontal extent of the stack is preferably such that a lower most article of the stack is removed and travels downwardly with respect to the stack retaining means by a distance substantially equal to the thickness of an article.

Preferably, the or each projection comprises a blade member having a leading edge which is substantially transverse to the extent of the conveying means, and a trailing edge which tapers towards the conveying means.

The height above the conveying means of the leading edge of the projection is preferably not greater than the thickness of an article, and may be substantially equal to the thickness of an article.

Preferably, the trailing edge of the projection is arranged, in use, to support the next lower most article in the stack.

In use, the articles are preferably urged onto guide means arranged to guide the motion of the articles away from the stack.

There may be provided additional urging means to urge the articles onto the guide means. The urging means may comprise one or more pin members, which pin members may be driven by a chain and sprocket type drive.

The guide means may comprise a number of wires arranged to support articles from below.

Alternatively or additionally, the or each article may in use be inverted after removal from the stack, by co-operation of the articles with a retaining member, which retaining member extends partly around a pulley of the conveying means, and is spaced from the conveying means.

Preferably the or each article is supported by one or more support members which are fixed relative to the

pulley, to support the or each article as it travels around the pulley.

The support members may comprise projections fixed to the pulley. The fixed projections may be attached to or integral with a plate mounted on the side of the pulley, such that the fixed projections extend radially outward with respect to the pulley.

Preferably, there are provided two plates located either side of the pulley of the conveying means, or if two conveying means are used, each having its respective pulley, the pulleys may each have a plate, such that the conveying means extend between the plates.

Preferably, the fixed projections are spaced apart by an extent substantially equal to the spacing of the articles on the conveying means.

In a preferred arrangement, two conveying means are provided below the stack of articles, such that each conveying means supports the lower most article as it is removed from the stack, there being one conveying means located substantially either side of a centre of a lower most article.

Preferably, the motion of the two conveying means is synchronised, such that in use projections on the two conveying means arrive at the lower most article at substantially the same time.

There may be provided a conveyor support means arranged, in use, to support at least the portion of the conveying means directly below the stack, such that the

said portion of the conveying means extends at an angle below horizontal.

The conveyor support means may be adjustable such that the angle below the horizontal at which the said portion of the conveying means extends in use may be adjusted.

Preferably, the conveyor support means is adjustable pivotally with respect to a pulley of the conveying means.

The invention also includes a method of removing articles from a stack in a stack retaining means, the method comprising conveying the lower most article of the stack away from the stack on conveying means, the conveying means being arranged to convey the lower most article downwardly with respect to the stack retaining means at least until the said article is conveyed beyond a horizontal extent of the stack.

The invention may include any combination of the features or limitations referred to herein.

The apparatus may be carried into practice in various ways, but an embodiment will now be described by way of example only with reference to the accompanying diagrammatic drawings in which:

Figure 1 shows an embodiment of apparatus for the removal of articles from a stack;

Figures 2a to 2d show in more detail the stages of removal of an article from the stack shown in Figure 1;

Figure 3 shows an alternative embodiment of apparatus arranged to remove articles from a stack; and

Figure 4 shows a still further embodiment of apparatus arranged to remove articles from a stack.

Referring to Figure l, a de-stacking unit shown generally at 1 has a conveyor belt 2 on which are mounted projections 3. Each of the projections 3 comprises a blade member having a leading edge 4 which is substantially normal to the surface of the belt 2, and a trailing support edge 5. The belt 2 is driven by a pulley or wheel 6 and the belt 2 is arranged to extend around a nylon support 7 positioned to the side of the pulley 6. The support, commonly referred to as a follower, is pivotally mounted about the centre of the drive pulley 6. The de-stacker unit 1 is positioned below a substantially vertical stack of biscuits 8 held in a magazine 9. The position of the drive pulley 6 is arranged such that clockwise rotation of the pulley 6 results in a left to right movement of the portion of the belt 2 beneath the magazine 9. The support 7 is mounted relative to the pulley 6 such that the portion of the belt 2 directly below the stack 8 of biscuits is angled downwardly with respect to the stack 8. In addition, the profile of the support 7 is such that the portion of the belt 2 directly below the stack 8 of biscuits is substantially flat.

Turning to Figures 2a to 2d, in Figure 2a the leading edge 4 of the projection 3 approaches the lowermost biscuit 10 of the stack of biscuits as the pulley 6 drives the belt beneath the stack 8. In Figure 2b the leading edge 4 of the projection 3 has contacted biscuit 10 which begins to move to the right. In addition, because the belt 2 is angled downwardly at this point with respect to

- 1 - the stack 8 the biscuit 10 is made to move progressively downwards and to the right of the stack. In Figure 2b, it can be seen that the next lower most biscuit 11 is supported at this point both by the previous biscuit 10 and the trailing support surface 5 of the projection 3.

In Figure 2c, the biscuit 10 is almost beyond the horizontal extent of the stack 8 and the next lower most biscuit 11 is almost completely supported on the trailing support surface 5 of the projection 3. At this point, the biscuit 10 is being supported on parallel guide wires 12 and is urged onto the guide wires 12 by pins 13 which are driven in synchronised position with the leading edge 4 of the projections 3 by an endless sprocket and chain.

In Figure 2d it can be seen that biscuit 10 is completely supported on the wires 12 and biscuit 11 is entirely supported on the trailing surface 5 of the projection 3.

From the sequence shown in Figures 2a to 2d, it can be seen that the leading edge 4 of the projection 3 moves to abut the lower most biscuit 10 in the stack and push the biscuit 10 from beneath the stack. As the lower most biscuit 10 is removed the support surface 5 of the projection 3 moves under the next biscuit 11 in the stack and supports the stack of biscuits progressively across the whole width of the biscuit. Due to the below- horizontal angle of the belt 2 as it travels beneath the magazine, the lower most biscuit and the biscuit stack descend at a constant speed relative to the speed of the belt. When the bottom biscuit has cleared the right hand edge of the magazine it is supported by the two wires 12, pins 13 being in synchronised position with the leading edge 4 of the projections 3 to push the biscuit along the

support wires 12. At this point, the vertical edge 4 of the following projection 3 is brought to abut the next biscuit 11 in the stack and the procedure is repeated.

The downward speed of the stack is determined by the angle of the belt below horizontal for any given belt speed. Thus various sizes and thicknesses of biscuit can be accommodated by varying the spacing between the projections on the belt and both the angle and speed of the belt. The range of biscuits that can be accommodated by one belt will primarily be determined by the height of the leading edge of the projections which must be no greater than the thickness of the biscuit and is preferably substantially the same as the thickness of the biscuit.

Turning now to Figure 3, this shows an alternative embodiment of apparatus to remove articles from a stack in which the biscuits are inverted after removal from the stack, i.e. to present the underside of the biscuits in the stack as the upperside for the next stage in a production process. In this embodiment an arcuate retaining member 14 is provided adjacent to the surface of the belt 2 which follows the belt 2 around the drive pulley 6 in order to retain the biscuits on the surface of the belt 2 as they travel around the pulley 6. The inverted biscuits are then presented to guide wires 12 below the pulley 6 and are urged along by contact with driven pins 13.

In Figure 4, a further embodiment of apparatus for removing articles from a stack includes the addition of a circular plate 15 mounted on the side of pulley 6. The plate 15 has fixed radially extending pins 16, the spacing of which is substantially equal to the spacing of the

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biscuits on the belt. As the biscuits travel around the pulley between the belt 2 and the retaining member 14, the biscuits are prevented from falling forwards and potentially jamming or breaking by the pins 16. Angular adjustment of the plate 15 on the pulley 6 may be achieved using a conventional slot and screw arrangement shown generally at 17. If a single pulley is used there is preferably a plate 15 mounted on each side of the pulley. If two pulleys are used there is preferably a plate 15 mounted on the outer surface of each of the two pulleys, with the belts extending between the plates 15.

Since the lowermost biscuit in the stack is removed downwardly, as well as horizontally, the stack as a whole maintains a constant downward motion which is not arrested at any time during the de-stacking process. Since the stack of biscuits is not undergoing a start-stop vibration there is less likelihood of damage to the biscuits.

It will be appreciated that the projections 3 are made sufficiently flexible to follow the path of the belt 2.

An advantage of using a belt as the conveying means is that the belt with its associated projections 3 can easily be changed when this is required to suit a different type of biscuit.