GB2167569A - 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 and the conveying means for transporting each article together with the drive required for the conveying means is supported entirely by the weighing apparatus 37. The conveying means comprises upper and lower transporting means, e.g. belts 27,28 driven in unison between which each article is held during the weighing cycle. <IMAGE>

Description

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 invervals 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 characteristics ofthe article and/or to determine its acceptance 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/or fragile 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 damage to the container or contents and to this end existing machines emplace or gently slide the package 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 shou Id not be subjected to forces u nrelated 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 1 00mm, these dimensions being consistent from package to package but when containing the product have a thickness, when resting on any weighing means, which varies from the container thickness of about mm 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 meansfortransporting each article together with the drive required for the conveying means is supported entirely by the weighing apparatus, wherein the conveying means comprises upper and lower transporting means between which each article is held during the weighing cycle.

Preferably the conveying means comprises at least one driven belt to 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.

It is also preferred that 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.

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 connection.

In the preferred embodiment of the invention the conveying means are 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.

By way 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 forthe articles to be weighed in accordance with the invention; Figure 4 is a plan view of the machine of Figure 3; 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.

Referring to Figures 1 and-2, packages from an outlet conveyor 1 of, for example, a filling and sealing machine 2 which is controlled to supply a substantially continuous, evenly spaced and correctly orientated as far as possible, sequence of pack ages 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 and made of woven nylon run on rollers 9 and 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 over fixed platforms 13 and 14 and the intermediate platform 15 ofthe weigh cell 18. The bands7 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 isthen 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 an operator with an interval for the removal of visually unsatisfactory packages.

There are disadvantages in the use of the above form of machine 5, both in transporting and weighing. As is apparent from the above description, it is usually convenient to use handling means i.e.

the inlet conveyor 4 to present a package to weighing conveyor 6 in a horizontally flat aspect, that is with the larger surfaces 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 two 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 itto glide away from the conveyor and/orto cause upward or downward force on the weigh cell when on the platform 15 and thereby give false indications of weight.

Again, it is clear that, in order to 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 ifthe 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 1 5 which may cause a frictional force on the package and delay its forward movement eventually causing successive packages to foul each other.

Again, it may happen that a damaged package arrives at conveyor 6 and its contents may spill onto the conveyor and fall into the moving and other parts of the machine or foul the weigh cell eventually causing it to give false indications.

In order to 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 manner to that shown in Figures 1 and 2, they are restrained while on a conveyor corresponding in sequence to conveyor 6 described above so that they 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 2but including the novel weigher/conveyor 20,37 shown in block form.

The weigherlconveyor 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 together with intermediate apparatus, on the platform 36 of a weigh cell 37. It will be appreciated that this embodiment is by way example andweigh cells other than oftheform shown and different methods of engineering may result in different construction detail. 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 any further items which have to be supported by the 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 about 42. At their upper ends arms 44,45 carry further bearings 63, 64 respectively and within these a further shaft 76 can 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 similarto 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.

Afurther 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 convenient to the weigh cell platform 36 may be placed above and below one of the bars 60 to 61 to limit the 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 ofthe 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 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 effect 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.

Claims (8)

1. Aweighing 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 the weighing apparatus, wherein the conveying means comprises upper and lower transporting means between which each article is held during the weighing cycle.

2. Aweighing machine as claimed in Claim 1, wherein the conveying means comprises at least one driven belt to 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.

3. Aweighing machine as claimed in Claim 2, 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.

4. Aweighing machine as claimed in Claim 3, wherein the or each upper belt is driven in unison with the or each lower belt.

5. Aweighing machine as claimed in Claim 4, 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.

6. A weighing machine as claimed in any one of the preceding claims, wherein the conveying means are offset to one side of the weighing apparatus whereby the article transported by the conveying means is weighed in cantileverfashion.

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

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