EP0233008A1

EP0233008A1 - Product group separation system

Info

Publication number: EP0233008A1
Application number: EP87300676A
Authority: EP
Inventors: Trevor Barrie Hoyland
Original assignee: Thurne Engineering Co Ltd
Current assignee: Thurne Engineering Co Ltd
Priority date: 1986-01-28
Filing date: 1987-01-27
Publication date: 1987-08-19
Also published as: GB8602024D0; JPS62244861A

Abstract

A jump conveyor for producing separated groups of slices produced by a slicing machine (5,6) comprises a support (47) to receive individual slices, a multi-element conveyor (73) intercallated with the support (47), and a drive (91) to move the multi-element conveyor (73) up and down. The multi-element conveyor (73) moves continuously with its conveying surface beneath the support (47) whilst the support receives individual slices to form a group, and then, upon actuation of the drive (91), the multi-element conveyor (73) moves upwards, engages the group of products and carries it away from the support (47). By operating the drive (91) at a speed sufficient to induce a reaction force of at least 3g between the conveyor (73) and the slices it is possible to obtain substantially no slip between them and the conveyor. This enables the slicing machine (5,6) to operate at high speed.

Description

This invention relates to a system for separating a continuous stream of products into groups of products. Conventionally this operation has been performed by what is known as a jump conveyor.
Typically a jump conveyor is located downstream from a slicing machine which produces slices of a product such as cheese, meat, or meat product. Commercial slicing machines operate continuously to produce slices at a constant rate whilst an entire piece of produce is sliced. The jump conveyor is usually located so that slices cut by the blade of the slicing machine fall directly onto its conveying surface. A number of slices to form a group fall onto the jump conveyor and then, the jump conveyor accelerates to move the group of slices in the period of time that exists between two successive slices being cut from the product. The jump conveyor may be stationary whilst it receives the slices to form each group to form an upright stack of slices or, alternatively, the jump conveyor may move at a slow speed whilst receiving the slices to form each group to form a shingled group of slices.
In practice it is usually the jump conveyor which is the limiting factor in determining the maximum rate of slicing. Part of the reason for this is naturally the inertia of the conveying band and its drive system but a more serious problem is that the groups of slices slip on the jump conveyor when it accelerates. With the high acceleration required for high speed operation this problem increases. With existing jump conveyors the maximum rate of slicing that can be achieved depends, at least to some extent, on the product being sliced. Some products can sliced at speeds as high as 500 slices per minute but, more usually the maximum speed is nearer 250 slices per minute. In contrast to this, slicing machines have a potential maximum speed of at least 1200 slices per minute and therefore it is desirable to be able to provide a product group separation system which is capable of operating at such speeds.
Specific proposals for other product separations systems for use with slicing machines are disclosed in US-A-3965783 and US-A-28127932. US-A-3965783 discloses a system in which a stream of product slices cut by the slicing machine are fed in one direction by a ribbon conveyor. Rollers of a roller conveyor for moving the product in a direction transverse to the one direction are intercallated between the ribbons of the ribbon conveyor. The roller conveyor is movable upwards and downwards to lift the product from the ribbon conveyor and move it sideways to a downstream output conveyor. US-A-2812792 discloses a system in which slices cut by a slicing machine fall onto a set of spiked rails. End rollers of a cantilevered multi-element conveyor are intercallated between the spiked rails and are movable upwards and downwards. Upward movement of the end rollers lifts the slices off the spiked rails and forwards movement of the multi-element conveyor conveys the products away. The slicing operation is interrupted to allow sufficient time for the cantilevered conveyor to lift and convey the products away. This system is not capable of operating at a higher speed without damaging the slices of product.
According to this invention a product group separation system comprises a product support to receive individual products, a multi-element conveyor intercallated with the support, and a drive for moving the multi-element conveyor up and down which is capable of moving the conveyor upwards with a velocity sufficient to induce a reaction force of at least 3g between the product and the conveyor, the arrangement being such that, in use, the multi-element conveyor moves continuously with its conveying surface beneath the support whilst the support receives individual products to form a group, and then, upon actuation of the drive, the multi-element conveyor moves upwards, engages the group of products and induces a reaction force of at least 3g between the multi-element conveyor and the product to provide, substantially slip-free contact between the product and the multi-element conveyor a2 the conveyor carries the product away from the support, the drive subsequently lowering the multi-element conveyor to allow the support to receive subsequent products.
Products may be fed to the product group separation system directly from a workstation or may be fed via an upstream conveyor. Preferably the product group separation system is arranged to handle slices of a product and, in this case, the product group separation system is located immediately downstream from a slicing machine and slices cut by the slicing machine fall directly onto the support.
The support may comprise a number of parallel rails which are fixed in space with the multiple elements of the conveyor interleaved between them. In this case the slices of product are formed into stacks on the fixed rail before being transported by the multi-element conveyor. Alternatively the support also comprises a multi-element conveyor. In this case the support multi-element conveyor has its elements interleaved with the elements of the other upwardly and downwardly movable multi-element conveyor. The support multi-element conveyor may run in the same direction as the upwardly and downwardly movable multi-element conveyor but at a lower speed to form shingled groups of slices or, alternatively it may run in the opposite direction to provide better registry between slices in a stack. As slices are cut in a slicing maching they have both vertical and horizontal components of movement. As the height of the stack increases the distance the slices travel after being sliced reduces and this means that they are displaced horizontally. By moving the stack as it is formed towards the slicing machine to compensate for the horizontal displacement it is possible to get an upright stack of slices in good register with one another.
Preferably the multi-element conveyor is arranged parallel to the support and is arranged to maintain its orientation constant as it moves up and down. This ensues simultaneous contact of the elements of the multi-element conveyor with the lower surface of the product which distributes the reactive force generated between the multi-element conveyor and the product over the entire base of the product. Preferably the multi-element conveyor includes individual idler pulleys which are free to rotate relative to one another. This prevents any build-up of meat or other product on the idler pulleys causing extreme variations in tension in the elements of the conveyor.
The multi-element conveyor, or conveyors, may be formed by ribbons, round-section belts, or chains. It is also possible to form the individual elements of the upwardly and downwardly movable conveyor with protruding spikes which also help to prevent relative movement between the groups of product and the conveyor.
With the arrangement in accordance with this invention the elements of the upwardly and downwardly movable multi-element conveyor are moving both upwards and forwards at the time that they engage the lower surface of a product on the support. This impact between the elements of the conveyor and the lower surface of the group of products causes a reaction force of at least 3g and often as high as 30g. This increases the friction between them and so prevents relative slip occurring. Naturally when the conveying surface of the conveyor includes spikes this effect is enhanced still further. When the product is a group of slices the impact between the elements of the conveyor and the lower surface of the group of slices also consolidates the group of slices and so helps prevent adjacent slices sliding over one another as the group is accelerated. We have found that the separation between adjacent groups of products can be improved by a factor of three or more using an arrangement in accordance with this invention, as compared to a conventional jump conveyor. Since the elements of the conveyor move continuously in the conveying direction its inertia and that of its drive does not affect the rate of acceleration of the groups of product. As a result of driving the conveyor upwards with sufficient velocity to eliminate slip between the groups of product and the conveyor it is possible to be confident of the precise location of any group of product at any instant as it moves away to a downstream operation and this facilitates that operation and avoids the need for additional product sensors and positioning means.
Examples of apparatus in accordance with this invention will now be described with reference to the accompanying drawings, in which:-

Figure 1, A, B and C show a sequence of diagrammatic partial sections illustrating the conveyor lifting a stack of slices from a stationary platform in a first example; and,
Figure 2 is a sectional elevation through a second example.

In the first example slices 1 of product collect from the output of a slicing machine (not shown) on a platform 2 formed by a number of parallel bars which are fixed in space. Belts 3 which are part of a high speed conveyor are located in the spaces between adjacent rails 2 and are movable upwards and downwards. The belts of the high speed conveyor are driven continuously typically at a speed of 100 m/min and are normally located beneath the surface of the rails 2 as shown in Figure 1A.
When the required number of slices have been collected by the rails 2 the belts 3 are lifted and moved into position above the top of the fixed rails 2. The belts 3 engage the lower surface of the stack of slices and carry them away.
The belts 3 are lifted rapidly and this causes a substantial increase in the reaction force between the lower surface of the stack of slices 1 and the conveying surface of the belt 3 which increases the friction that exists between the two and so substantially prevents any slip from occurring between the stack of slices and the belts 3. As an example of this consider the situation where the belts 3 are lifted by a distance of 9 mm in a time of 25 ms. Assuming that the belts 3 are subjected to constant acceleration in a vertical direction then their acceleration can be deduced as follows:
9 = ½a(0.025)² therefore a = 28,800 mm/sec² = 2.94 g
The time before impact, T_i =
^½ = 20.4 ms
The approximate effect on the bottom of the stack of slices can therefore be thought of as the bottom of the stack moving a vertical distance of 3 mms in 4.6 ms. Therefore, the acceleration A that the bottom of the stack is subjected to is given by:
A =
= 283.554 mm/sec² = 30 g
Thus by approximate calculation the reaction force between the bottom of the stack of slices and the belts 3 is increased some thirty times by the impact that occurs between the belts and the bottom of the stack of slices which greatly increases the resistance to slip that exists between them. Clearly if the slices of meat were subjected to such a high acceleration as 30 g this may cause damage but there is usually some inherent elasticity in the belts 3 or ribbons forming the conveyor which reduces the impact to acceptable limits whilst, at the same time still causing a substantial increase in the friction that exists between the belts and the stack of slices. With an arrangement in accordance with this invention we have found it possible to operate a slicing machine at speeds of 1200 slices per minute and to create stacks at a rate of 140 stacks per minute with outstanding pack separation.
Figure 2 illustrates a practical embodiment of the present invention. In this example slices of meat cut by a slicing machine 5 including a blade 6 fall onto a belt conveyor formed by a series of inclined belts 47 running on rollers 45 and 46. The roller 45 is driven by a conventional stepper motor drive (not shown) which enables the belt to be driven to the left or to the right as shown in Figure 2 at a required rate. The axis of the rollers 45 and 46 is fixed in space. Typically, the belts 47 run towards the right as shown in Figure 2 to form a shingle of slices. They may also remain stationary to form a stack of slices or be moved to the left even more slowly to create a stack in substantially perfect register.
A ribbon conveyor including ribbons 73 and a drive drum 58 runs over edges 70, idler rollers 67 and a tensioning roller 68. The ribbons 73 are interleaved with the belts 47. The entire ribbon conveyor is movably mounted in the vertically direction on a movable carriage 90 which is driven upwards and downwards by a pneumatic cylinder 91 having a stroke of 12.5 mm and a diameter of 62 mm. The individual idler rollers 67 are all rotatably journalled on a shaft 68 which is also freely rotatable in end bearings (not shown). One of the idlers 67 may be keyed onto of the shaft to ensure that it rotates.
A take away conveyor formed by belts 10, a drive roller 12, idler and tensioning rollers 16 and a further idler roller 17 operates continuously, at the same velocity as the ribbon conveyor. The upper surface of the belts 10 is above the upper surface of the ribbons 73 when the ribbon conveyor is in its lowermost position but below the upper surface of the ribbons 73 when the ribbon conveyor is in its uppermost position.
In use groups of slices build up on the belts 47 and, as soon as the correct number of slices have been accumulated the pneumatic cylinder 91 is operated to lift the ribbon conveyor rapidly. In practice the cylinder 91 is arranged to move the conveyor through a distance of 9 mm and this is achieved in a time of 25 ms. The ribbons 73 engage the lower surface of the group of slices in an analogous fashion to the first example and move the stack rapidly towards the right as shown in Figure 2. The pneumatic cylinder 91 is again operated to lower the ribbon conveyor and this deposits the group of slices onto the belts 10 of the take-off conveyor and allows the next slice to fall onto the belts 47. The idler roller 17 at the downstream end of the take-off conveyor is connected to a pivoted arm 18 which can pivot through about 25 degrees to supply the groups of slices to two different destinations.
The take away conveyor may have a variable speed and so slow down after accepting the group of products. Whilst it is desirable for the ribbon conveyor to be operating at high speed when it engages a group of products and moves that group away as rapidly as possible it is also possible for it to slow down before transferring the product to the take away conveyor.

Claims

1. A product group separation system comprising a product support (47) to receive individual products, a multi-element conveyor (73) intercallated with the support (47), and a drive (91) to move the multi-element conveyor up and down, the arrangement being such that, in use, the multi-element conveyor moves continuously with its conveying surface beneath the support whilst the support receives individual products to form a group, and then, upon actuation of the drive, the multi-element conveyor moves upwards, engages the group of products and carries it away from the support, the drive subsequently lowering the multi-element conveyor to allow the support to receive subsequent products, characterised in that the drive (91) is capable of moving the conveyor (73) upwards with a velocity sufficient to induce a reaction force of at least 3g between the product and the conveyor (73) so that substantially no slip occurs between the product and the multi-element conveyor (73).

2. A product group separation system according to claim 1, arranged to handle slices of a product and located immediately downstream from a slicing machine (5,6) so that slices cut by the slicing machine (5,6) fall directly onto the support (47).

3. A product group separation system according to claim 1 or 2, in which the support (47) comprises a multi-element conveyor having its elements interleaved with those of the upwardly and downwardly movable multi-element conveyor (73).

4. A product group separation system according to claim 3 when dependent on claim 2, in which the support multi-element conveyor (47) is arranged to run in the same direction as the other multi-element conveyor (73) but at a lower speed to form shingled groups of slices.

5. A product group separation system according to claim 3 when dependent on claim 2, in which the support multi-element conveyor (47) is arranged to run in the opposite direction to the other multi-element conveyor (73).

6. A product group separation system according to any one of the preceding claims, in which the multi-element conveyor (73) is parallel to the support (47) and is arranged to keep its orientation constant as it moves up and down.

7. A product group separation system according to any one of the preceding claims, in which the individual elements of the upwardly and downwardly movable conveyor (73) are formed with protruding spikes which, in use, are driven into the product by the reaction force generated between the product and the conveyor.

8. A product group separation system according to any one of the preceding claims, in which the multi-element conveyor (73) includes individual idler pulleys (67) which are free to rotate relative to one another.