GB2137365A

GB2137365A - Portion weighing apparatus

Info

Publication number: GB2137365A
Application number: GB08408160A
Authority: GB
Inventors: David William Openshaw
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-03-29
Filing date: 1984-03-29
Publication date: 1984-10-03
Also published as: GB8408160D0

Abstract

A weighing apparatus comprises an initial plurality of weigh cells 20 and one or more further pluralities of weigh cells 22. Material from one or more of the weigh cells 20 is delivered to a pocket 16 which then receives material from one or more of the weigh cells 22 to bring the total weight to at least a required predetermined value. <IMAGE>

Description

SPECIFICATION Portion weighing apparatus This invention relates to apparatus for weighing portions of substances and in particular for accurate weighing of portions of food substances.

It is a requirement that most packaged foodstuffs must carry an indication as to the weight of the contents of the package. Legislation in the United Kingdom provides that it is an offence if the contents of the package should be less than the stated weight.

In order to meet these demands it has been common practice to ensure that packaged foodstuffs are significantly overweight rather than obtain close control of portion weights. With the increasing cost of foodstuffs there is an economic advantage in closely limiting the weight of the portion to match the stated weight.

The present system of high speed weighing portions to a high degree of accuracy consists of a plurality of weigh cells arranged in a circle. The weigh cells are adapted to deliver different weights of product. To obtain a portion product is collected from the best combination of weigh cells which when totalled is closest to the required weight. The speed of this kind of system is dependent on the time taken to combine the product from selected weigh cells into a single portion and that time is itself, of course, dependent on the distance that each part of the portion must travel from a selected weigh cell in order to be combined into the final portion.

Furthermore, although the accuracy of the system can be increased by including a large plurality of weigh cells offering a large number of different weights of product, the more weigh cells that are used to form a portion the longer the time taken over the creation of each portion.

The present invention has been made with these problems in mind.

According to the invention there is provided a portion weighing apparatus comprising portion receiving means, an initial plurality of weigh cells, one or more further pluralities of weigh cells, means for causing delivery of material to the portion receiving means from one or more of the weigh cells of the initial plurality, the amount of material so delivered being less than a predetermined weight and means for causing delivery of material to the portion receiving means from one or more of the weigh cells of the or each subsequent pluralities to bring the total weight of material in the portion receiving means to an amount at least equal to said predetermined weight, there being means for discharging material from said portion receiving means.

In a preferred embodiment of the invention the portion receiving means is mounted for movement sequentially past each plurality of weigh cells.

Preferably material delivered from the combintion of weigh cells selected of each plurality is delivered substantially simultaneously. Discharge of material from the portion receiving means is preferably arranged to take place after the portion receiving means has been moved away from the weigh cells.

After emptying the portion receiving means is preferably returned to receive a further supply of material from the weigh cells.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in-which: Figure 1 shows diagrammatically, a part of a portion weighing apparatus; Figure 2 is a side elevation of a preferred form of portion receiving means; and Figure 3 is a diagrammatic pian view of another part of the apparatus.

Referring to the drawing a plurality of pockets 10 are arranged on an endless conveyor for stepwise movement in the direction af arrow.12. Each pocket has an open top 14 and walls 16 which are inclined downwardly and inwardly to a discharge orifice 18 which has a releasable closure (not shown).

Afirst plurality 20 of weigh cells, four in the embodiment as illustrated, is arranged above the conveyor. The area occupied by the weigh cells 20 matches the area of the open top of a pocket 10. A second plurality 22 of weigh cells, six in the embodiment illustrated, is arranged beside and downstream of weigh cells 20. The area occupied by weigh cells 22 also matches the area of the open top of a pocket 10.

Each weigh cell comprises a container, the bottom of which consists of a weigh pan. Each container is adapted to receive a quantity of material from a supply not shown. Means such as a sliding shutter or camera lens type shutter is incorporated in the weigh pan so that, upon actuation of the shutter the weigh cell is emptied. The actuation of the shutters and the selection of which shutters are actuated is preferably controlled electronically.

The apparatus operates as follows. Stepwise actuation of the conveyor brings an empty pocket beneath the first plurality of weigh cells 20. The shutters of one or more cells are actuated to deliver a quantity of material that is close to, but below, the predetermined weight of material required in the pocket. If more than one cell is used then the cells that are used all empty simultaneously. The con veyorthen moves the pocket under the weigh cells 22. Electronic control means having noted the difference between the weight of material already delivered and the predetermined weight selects a combination of one or more cells 22 and actuates the shutters thereof so as to deliver a quantity of material simultaneously to bring the weight of material in the pocket to the required weight or the minimum above the required weight as possible.In other words the cells 20 deliver the bulk of material and the fine adjustment is effected by cells 22. The filled pocket is then moved away from cells 22 and is emptied into a package at a suitable point downstream. After emptying the pocket is returned by the conveyor to the weigh cells to receive another portion.

It will be appreciated that with a continous series of pockets on the conveyor, when a filled pocket is moved from beneath the weigh cells, another empty pocket moves in to take its place.

The invention is not limited to the above described embodiment; many variations can be made. The number of weigh cells at each station can be varied depending upon the accuracy of weighing required.

In addition the number of groups of weigh cells need not be two as illustrated but can, if desired, be increased. The dimensions of the pockets, in particularthe angle of the walls and the pocket depth can be adjusted to achieve the requisite speed of delivery of material therefrom.

Means may be provided in the weigh cells for positively urging material therefrom and into the pockets instead of relying solely upon gravity. In addition similar means may be provided for emptying the pockets. It is preferred that the pockets are not emptied until they have travelled sufficiently far downstream of the weigh cells for the material therein to have settled at the bottom of the pocket.

With the tops of the pockets being very close to the weigh cells the time taken for material to fall into the pocket from the weigh cells is reduced to a minimum. Very high speeds of portion weighing can be achieved with the invention whilst retaining a high degree of accuracy.

In the embodiment described material is only delivered from weigh cells to a pocket stationed underneath. If desired it is possible for material to be delivered from weigh cells to adjacent pockets on either side instead of directly underneath.

One of the factors governing the speed of the apparatus is the time taken for material to be discharged from a pocket. If it is arranged for the pocket only to discharge at one specific station then the pocket must remain at that station until it is empty. For accuracy of weight of material discharged from a pocket the time for discharge from the pocket should be as long as possible to ensure that all the contents have been discharged.

In order to deal with this problem a pocket as illustrated in Figure 2 having an inclined discharge chute 30 can be used. As shown in Figure 3 the pocket is arranged with other like pockets to be moved, after it has received material from the weigh cells, around an arcuate path 32 with the inclined chute 30 directed towards the notional centre of curvature 34 of the path 32. As the pockets move around the path 32 the lower end of chute 30 only moves a small distance so that material can be collected from a pocket during the time it travels around the path. In this way the time during which material is received from a pocket is increased without reducing the speed of movement of the pockets.

Claims

1. A portion weighing apparatus comprising portion receiving means, an initial plurality of weigh cells, one or more further pluralities of weigh cells, means for causing delivery of material to the portion receiving means from one or more of the weigh cells of the initial plurality, the amount of material so delivered being less than a predetermined weight and means for causing delivery of material to the portion receiving means from one or more of the weigh cells of the or each subsequent pluralities to bring the total weight of material in the portion receiving means to an amount at least equal to said predetermined weight, there being means for discharging material from said portion receiving means.

2. Apparatus as claimed in Claim 1, wherein the portion receiving means is mounted for movement sequentially past each plurality of weigh cells.

3. Apparatus as claimed in Claim 1 or Claim 2, wherein means are provided whereby material delivered to a portion receiving means from the selected weigh cells of each plurality of weigh cells is delivered substantially simultaneously.

4. Apparatus as claimed in any preceding claim, wherein means are provided for discharging material from the portion receiving means after said portion receiving means has been moved away from said pluralities of weigh cells.

5. Apparatus as claimed in any preceding claim, wherein means are provided for returning portion receiving means from which material has been discharged to receive fresh material from said pluralities of weigh cells.

6. Apparatus as claimed in any preceding claim wherein material is deposited into portion receiving means below said weigh cells.

7. Apparatus as claimed in any preceding claim, wherein the portion receiving means are arranged to follow a substantially arcuate path during which material is discharged from said portion receiving means.

8. Apparatus as claimed in Claim 7, wherein each portion receiving means has a discharge chute arranged to be directed towards the centre of curvature of the arcuate path.

9. A portion weighing apparatus substantially as described herein with reference to the accompanying drawings.