GB2167570A - Weighing machine - Google Patents

Abstract

The invention concerns a weighing machine in which a succession of articles, e.g. packages or other items, is conveyed across weighing apparatus. The conveying means for transporting each article together with the drive 35 required for the conveying means is supported entirely by a weigh cell 37. The conveying means preferably comprises transporting means which supports the article being transported, and the conveying means may comprise upper and lower transporting means 27,28 between which each article is held during the weighing cycle. <IMAGE>

Description

1 GB 2 167 570 A 1

SPECIFICATION

Weighing machines The invention relates to weighing machines. More particularly,the invention relates to a form of check-weighing machine in which articles whose weights are to be checked are arranged to pass at substantially constant intervals of time over a weighing device hereafter called a "weigh cell", the output of the weigh cell representing the weight or, by suitable processing, the volume or other charac teristics of the article and/or to determine its accept ance by or rejection from the conveyor line by suitable means. These means are not the subject of the invention.

As will be understood, the variety of forms of package to be handled in large quantities by the consumer product and other industries is very great and appropriate machinery for such handling is required to suit the package although, in some cases, what is nominally a standard machine may only require minor modification or adjustment to make it suitable for a variety of forms of package.

The forms of package may have rigid or semi-rigid containers as, for example, cans of peas or boxes of sweets or chocolates where, despite the movement of product within the container, the external shape of the package is substantially invariable. However, there exist many forms of package where the product container may be non-rigid and/orfragile and again may contain a product which can change its position within the container so that the external contour of the container may change from package to package or may change its contour as it is transported from point to point by the handling machinery as, for example, packages of dry powder soup mixes, potato crisps, dried potato, packs of sweets and the like. Such packages must be handled carefully so that there is no gross deformation or 105 damage to the container or contents and to this end existing machines emplace or gently slide the pack age on to conveying or weighing means.

Again, as will be appreciated from the above examples, packages may be extremely light, the contents of the container weighing only a few tens of grammes and the containers only a few grammes. It thus important that, in the weighing operations, the packages should not be subjected to forces unre lated to their weights and that the contents should be prevented, as far as is possible, from tumbling during the weighing operation. An unrelated force as above may occur and be particularly objectionable when the package is thin and light and to be transported and weighed at high speed. It is well known that the packaging industries require such speeds to be increased as far as possible. An example of such a package would be a package of powdered soup mix which might be contained in a sealed metal foil or treated paper envelope or bag which might have sides of dimensions 120mm by 10Omm, these dimensions being consistentfrom package to package but when containing the product have a thickness, when resting on any weighing about 1/2mm at the outer edges to perhaps 20mm at some other point on the package, depending on the nature of the contents and its distribution within the package resulting from previous handling. Required speeds of operation may be up to 300 per minute.

According to the invention there is provided a weighing machine in which a succession of articles is conveyed across weighing apparatus and the conveying means for transporting each article together with the drive required for the conveying means is supported entirely by a weigh cell.

Preferably the weigh cell has a platform, and the conveying means which is supported entirely by the weigh cell comprises a drive motor mounted on the weigh cell platform, a drive shaft connected to the drive motor, at least one driven belt to support the article being transported, and apparatus intermediate the drive shaft and the or each driven belt.

The conveying means preferably comprises trans- porting means, e.g. at least one driven belt, which supports the article being transported.

In one embodiment of the invention the conveying means comprises upper and lower transporting means between which each article is held during the weighing cycle. The conveying means may comprise at least one driven beItto support the article being transported with at least one further belt above the article which upper belt, in use, rests in contact with the article to restrain it against movement relative to the supporting belt or belts.

In this case the or each upper belt may be mounted for movement to vary the vertical gap between the upper and lower belts, which movement is effected by the article being weighed as it 100 enters said gap.

Preferably, the or each upper belt is driven in unison with the or each lower belt by means of a drive connection from the drive means to the or each lower belt.

Conveniently a parallel linkage is provided between the drive to the lower belt or belts and the interconnected drive to the or each upper belt whereby the gap between the upper and lower belts may be varied without breaking the drive connec- tion.

In the preferred embodiment of the invention the or each driven belt of the conveying means is offset to one side of the weighing apparatus whereby the article transported by the conveying means is weighed in cantilever fashion.

The weighing machine defined above is particularly suitable for weighing packages of varying thicknesses and profiles.

Byway of example, an existing weighing machine and a weighing machine in accordance with the invention will be described with reference to the accompanying diagrammatic drawings in which:- Figure 1 is an elevation of an existing weighing machine including conveying means for the articles to be weighed; Figure 2 is a plan view of the machine of Figure 1; Figure 3 is an elevation of a weighing machine including conveying means for the articles to be weighed in accordance with the invention; means, which varies from the container thickness of 130 Figure 4 is a plan view of the machine of Figure 3; 2 - GB 2 167 570 A 2 Figure 5 is an elevation of the weighing portion of the machine of Figure 3; Figure 6 is a plan view of the weighing portion shown in Figure 5; and - Figure 7 is a section along line 7-7 in Figure 6. 70 Referring to Figures 1 and-2, articles, in this embodiment packages from an outlet conveyor 1 of, for example, a filling and sealing machine 2 which is controlled to supply a substantially continuous, evenly sp aced and correctly orientated as far as possible, sequence of packages 3 are fed to the inlet conveyor-4 of weighing machine 5. The packages 3 are in turn transferred to weighing, conveyor 6 which may be a form commonly known as a flat band conveyor. Two flat, light, thin and flexible bands 7 and 8, which have a width and thickness commensurate with the bulk of the package to be handled and may,for example, be 15mm wide and 2mm thick are made of woven nylon run on rollers 9and 10 which may be driven by a pair of pulleys 11 (one for each band 7, 8) and be tensioned by a further pair of pulleys 12, slide lightly overfixed platforms 13 and 14 and the intermediate platform 15 of the weigh cell 18. The bands 7 and 8 gather up a package and carry it across the upstream platform 13, then on to the weigh cell platform where at an instant, when preceding and succeeding packages are clear of 15, the package is weighed. It is then conveyed across the downstream platform 14, then to the outlet conveyor 16 of the weighing machine 5, and in turn to a further conveyor 17 by which it is transported for further processing e.g. labelling or final packing. Conveyors 4 and 16 may be of a wide flexible band variety and are provided for convenience in the design of the packaging line, for example, to provide 100 an operator with an interval forthe removal of visually unsatisfactory packages.

There are disadvatnages in the use of the above form of machine 5, both in transporting and weighing. As is apparent from the above description, 105 it is usually convenientto use handling means i.e. the inlet conveyor 4to present a package to weighing conveyor 6 in a horizontally flat aspect, that is with the largersurfaces facing upwards and downwards. At a rate of weighing 300 per minute a package travels at about 4 feet per second i.e. at about 3 miles per hour. While this may appear to be a very modest speed it is sufficient, with packages which are other than precisely flat and horizontal, to cause an aerodynamic force on the package and without any restraint on the package this may cause it to glide away from the conveyor and/or to cause upward or downward force on the weigh cell when on the platform 15 and thereby give false indications of weight. - Again, it is clearthat, in orderto impart a steady forward motion to the package, the bands 7 and 8 must maintain sufficient contact with the package and this may be prevented if the package is other than reasonably flat on its lower surface since, if it is not,-it may rest too heavily on platforms 13,14 or 15 which may cause a frictional force on the package and delay its forward movement eventually causing successive packages to fou I each other, Again, it may happen that a damaged package I.- arrives at conveyor 6 and its contents may spill on to the conveyor and fall into the moving and other other parts of the machine or foul the weigh cell eventually causing itto give false indications.

In orderto overcome at least the first of these, problems, we have produced novel means 20,37 (Figures 3 to 6) of conveying and weighing a variety of forms of package particularly of the kind with non-rigid containers. While packages 21 are carried towards weighing means in a similar mannerto that shown in Figures 1 and 2, they are restrained while on a conveyor corresponding in sequence to conveyor 6 described above so thatthey adopt a consistent attitude to the horizontal and provide a more consistent weight indication and again cannot glide away from the conveying means due to any aerodynamic forces as above. Further, in this embodiment, to overcome also the second of the above mentioned problems, the conveying means is offset from the driving and weighing means so that, in the event of the arrival of a package which is spilling its contents, the latter do not foul the machine but fall to a location from which they can be readily removed.

Figures 3 and 4 show a portion of a packaging line similar to the line of Figures 1 and 2 but including the novel weIgher/conveyor 20,37 shown in block form. The weigher/conveyor 20,37 is shown in detail in Figures 5 to 7. Packages 21 from the outlet conveyor 22 of, for example, a filling or sealing machine 23 which is controlled to supply a continuous, evenly spaced and correctly orientated as far as possible, sequence of packages 21 are fed to the inlet conveyor 24 of weighing machine 25.

The weigher/conveyor 20,37 is now described with reference to Figures 5 to 7. A conveying means comprising an upper belt 27 and two lower belts 26, 28 running on pulleys 33,34 and 31, 29 and 32,30 respectively, is mounted together with a motor drive 35 togetherwith intermediate apparatus, on the platform 36 of a weigh cell 37. In this embodiment the belts 26, 27, 28 are all round belts. It will be appreciated-that this embodiment is by way of example and weigh cells other than of theform shown and different methods of engineering may result in differrentcontruction detail.. However itis emphasised that the whole conveying means including the. belts, drive motor and intermediate apparatus is supported entirely by the weigh cell, and it is not just the belts 26, 27, 28 which are suppo rted by the weigh cell.

Two plates 38 and 39 are mounted rigidly on the weigh cell platform 36. The drive motor 35 is attached to a further plate 40 rigidly attached to platform 36 and is positioned so that it can drive a shaft 42 running freely in bearings 65, 66, rigidly attached to plates 38, 39 respectively, via for example a flexible coupling 41. The platform 36 and plates 38,39,40 may, of course, be replaced by a suitably machined casting to carry the above and anyfurther items which have to be supported bythe weigh cell and are part of the conveyor assembly.

Two arms 44,45 are carried by bearings 46,47 respectively on shaft 42 and can partially rotate freely about42. Attheir upper ends arms 44,45 carry further bearings 63, 64 respectively and within these 3 GB 2 167 570 A 3 a further shaft 76can rotate freely. The shafts 42 and 76 also carry identical meshing gears 48, 49 respectively so that shaft 76 is driven by shaft 42 and this drive is maintained when gear 49 is caused to perform a planetary motion about gear 48, such motion being caused during each weighing cycle by the package being weighed. This arrangement is capable of accommodating packages with varying profiles as described below.

Further bearings 50, 51 are attached to plates 38, 39 respectively and within these a shaft 43 similar to shaft 42 can rotate freely. The spacing of shaft 43 from shaft 42 will be dependent on the dimensions of the packages to be handled but the spacing is such that packages with a wide range of dimensions can be accommodated.

A further shaft 52 is also fixed to plates 38, 39 and carries bearings 53, 54 set into arms 55, 56, which are identical to arms 44, 45. Bearings 57, 58 are set into the upper ends of arms 55, 56 and carry a further shaft 59 which can rotate freely within 57, 58. Again arms 44,45 and 55, 56 respectively are connected by bars 60, 61, the bars being attached to the arms by, for example, suitable cap screws 71 (Figure 5) forming simple bearings to allow partial rotation of the bars relative to the arms. It will now be seen with reference to Figure 5 that the upper pair of shafts 76 and 59 can move synchronously vertically while arms 44, 45 and 55, 56 rotate partially about shafts 42 and 52 respectively. Stops 67, 68 attached as convenientto the weigh cell platform 36 may be placed above and below one of the bars 60 or 61 to limitthe vertical travel of shafts 76, 59 and their associated fittings.

The shafts 42, 43 further carry pulleys 29, 30 and 31, 32 respectively, and the shafts 76, 59 carry pulleys 34, 33 respectively; the pulleys in each case being rigidly but adjustably attached to the shafts, for example, by set screw means within the pulleys.

As mentioned above, the pairs of pulleys 29,31 and 33, 34 and 30, 32 are connected by the flexible belts 26, 27 and 28 respectively.

The motor 35 is driven to cause the upper lengths of the two lower belts 26, 28 to travel, in this example, from left to right and since gear 48 meshes with gear 49 the lower length of the upper belt 27 also travels from left to right.

It will now be seen that, as a package 21 is fed from conveyor 24, it will initially rest lightly on the belts 26, 28 and then be seized between the belts 27 and the belts 26, 28 and conveyed across the weigh cell. The stops 67, 68 are set to enable this seizure to occur in a smooth manner, bearing in mind the form of package being handled. The lower stop 68 may conveniently be set so that the lower length of belt 27 is, for example, 1 mm or 2mm above the upper lengths of belts 26, 28, and the portion of the upper stop 67 will depend on the maximum thickness of package to be weighed.

When a package 21 is approximately centrally positioned between shafts 42 and 43 and again before the arrival of a following package at the conveying means and again when a preceding package is clear of the conveying means, the package on the weigh platform is weighed.

The number of pairs of pulleys on shafts 42,43 and/or on shafts 76, 59 may be increased if the nature of the package requires such additional drive or support; again the pulleys may be replaced by rollers carrying flat belts if necessary. Such rollers may be profiled to improve contact with the package and again may be grooved to allow circular belt drives as when pulleys are used.

Since ' as described above, the weigh cell 37 carries and thereby supports the motor drive 35 to the conveying apparatus, power supply leads 69, fixed mechanically to the motor on the one hand and to the frame 70 of the machine on the other, are required and these must exert a negligible or a consistent eff ect on the weight indication of the weigh cell, when their effect can be ignored or compensated for. Light and flexible leads 69 are thus suspended between motor and frame or the leads may consist of flat, light and rigidly attached springs between the motor, or as convenient on the weigher/ conveyor assembly and frame. Similarly fixed vertical spiral springs to give a consistent upward or downward force on the weigh cell, which force may be offset by conventional means, may again be used. Such leads as described above now become part of the weigh cell.

The invention is not restricted to the specific details of the example described above with reference to Figures 3 to 7 of the drawings. For example, the conveying means may still comprise the upper belt 27 but only a single flat lower conveying belt to support the articles, e.g. packages or other items, being transported, instead of the two round lowar belts 26, 28.

In another embodiment, if the articles being handled are relatively heavy or will in any event remain stable in their position relative to the lower conveying means without the assistance of the upper conveying belt 27, the upper belt 27, together with the shafts 76, 59 and their associated fittings may be omitted, The articles will thereby be supported on the lowe conveying means only, which may comprise a single flat belt or the two round spaced apart belts 26, 28. The machine will prefer- ably be designed so that it can be simply and quickly modified.

However, in each case the conveying belt, or belts, together with the drive thereto, i.e. the motor 35 and the intermediate apparatus, is still supported entirely bytheweighcell.

Claims (11)

1. A weighing machine in which a succession of articles is conveyed across weighing apparatus and the conveying means for transporting each article together with the drive required for the conveying means is supported entirely by a weigh cell.

2. A weighing machine as claimed in Claim 1, wherein the weigh cell has a platform, and the conveying means which is supported entirely by the weigh cell comprises a drive motor mounted on the weigh cell platform, a drive shaft connected to the drive motor, at least one driven belt to support the article being transported, and apparatus intermedi- 4 GB 2 167 570 A 4 ate the drive shaft and the or each driven belt.

3. A weighing machine as claimed in Claim 1, wherein the conveying means comprises transporting means which supports the article being trans5 ported

4. A weighing machine as claimed in Claim.3, wherein the conveying means comprises upper and lower transporting means between which each article is held during the weighing cycle.

5. A weighing machine as claimed in Claim 4, - wherein the conveying means comprises at least one driven beitto support the article being trans ported with at least one further belt above the article which upper belt, in use, rests in contact with the article to restrain it against movement relative to the supporting belt or belts.

6. A weighing machine as claimed in Claim 5, wherein the or each upper belt is mounted for - movement to vary the vertical gap between the upper and lower belts, which movement is effected by the article being weighed as it enters said gap.

7. Aweighing machine as claimed in Claim 6, wherein the or each upper belt is driven in unison with the or each lower belt by means of a drive connection from the drive means to the or each lower belt.

8. A weighing machine as claimed in Claim 7, wherein wherein a parallel linkage is provided between the drive to the lower belt or belts and the interconnected drive-to the or each upper belt whereby the gap between the upper and lower belts may be varied without breaking the drive connection.

9. A weighing machine as claimed in anyone of the preceding claims, wherein the or each driven belt of the conveying means is offset to one side of the weighing apparatus wherebythe article transported by the conveying means is weighed in cantilever fashion.

10. A weighing machine as claimed in anyone of the preceding claims, wherein the articles to be weighed are packages of varying thicknesses and profiles.

11. A weighing machine substantially as hereinbefore described with reference to and as shown in Figures 3 to 7 of the accompanying drawings.

Printed in the UK for HMSO, D8818935, 4186, 7102. Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.