US3814195A - Weight quality control determination - Google Patents

Weight quality control determination Download PDF

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Publication number
US3814195A
US3814195A US00393387A US39338773A US3814195A US 3814195 A US3814195 A US 3814195A US 00393387 A US00393387 A US 00393387A US 39338773 A US39338773 A US 39338773A US 3814195 A US3814195 A US 3814195A
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United States
Prior art keywords
articles
weight
declared
balance
series
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Expired - Lifetime
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US00393387A
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English (en)
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P Gilbert
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Lever Brothers Co
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Lever Brothers Co
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Publication date
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01G—WEIGHING
    • G01G15/00—Arrangements for check-weighing of materials dispensed into removable containers

Definitions

  • a weighing apparatus consists essentiallyof a three [21] Appl 393387 pan balance with the pans at different pre-set distances from'a fulcrum. Preferably a second balance, [30] Foreign Application Priority Data an equal arm two pan balance is also provided. These Sept. 4, 1972 Great'Britain 40842/72 balances enable a method of Weight determination to be rapidly carried out to establish the maximum 521 vus. (:1 177/1, 177/200, [77/246 weight that can be marked on a given set of packs 511 11111. (:1.
  • nominal declared weight is used in this specification to define the weight declared to the con-. su'mer,,usually it is the weight marked on the pack. lt willbe recognised that when packs are filled by machinery to a'given weight, i.e., target weight, there will be a spread about this target weight, some packs being lighter and some heavier, and that this variation will usually be in accordance with the normal distribution curve. Good practice and in some cases legislation requires that a large proportion of the packs will contain at least the weight marked on the pack and generally,
  • target weight whichis greater than the nominal declared weight.
  • minimum difference between target weight and nominal declared weight is effectively defined by legislation in terms of the standard deviation of the normal distribution curve.
  • the target weight would be adjusted so that there was always the optimum minimum difference between the target weight and the nominal declared weight on the packet.
  • this requires calculation of the standard deviation and in practice this is usually difficult to effect sufficiently quickly and easily to be of use.
  • the present invention relates to a method and apparatus for this purpose.
  • the invention provides amethod of deerated between mean weight and declared weight
  • the term we use for the maximum safe value of the declared weight is often referred to as the risk point or a defined percentage of the normal distribution curve and may not be the same as the nominal declared weight marked on the pack. it is the maximum value which the nominal declared weight can safely be without infringing regulations or practice requirements.
  • weight legislation is interpreted by practice to require that 97% percent of production must be above the declared weight (the legal requirements on this differ from countermining the maximum safe value of declared weight g for a series of articles of nominal declared weight comprising:
  • the constant 2 usually lies between 1.5 and 3 and is proportional to the number of standard deviations toltry to country). This means that mean or target weight has to be 1.96 standard deviations above the declared weight. The two constants would be selected to achieve this requirement, and then from performing the method to obtain maximum safe value of declared weight we would compare the answer obtained with the nominal weight declared on the pack.
  • the nominal declared weight marked on the pack is greater than the value of declared weight obtained by the process of the invention, it means that these packs the pack, it means that the filling machine is putting more material in the pack than it needs to and should be adjusted accordingly.
  • the weight measurement can be made on a beam balance having a fulcrum and three weigh stations at different predetermined distances from said fulcrum, the first and second stations being arranged to act in opposition to one another and the third station providing a position for measurement of the maximum safe value of the declared weight.
  • the invention also provides a weighing apparatus for determining the maximum safe value of declared weight for a series of articles of nominal declared weight, comprising a beam balance having three 3 weigh stations effectively locatedat different-distances from a pivot point, said distances being in the ratio 1: (z 0.5/n): (z 0.5/n) where n is the number of articles in a sample group within the series'and z is a con It will be recognised that the larger the sample the greater the accuracy or significance of the determined safe maximum value of the declared weight. Where the subgroups consist of two articles, it is desirable that there should be at least four sub-groups to obtain a significant result. Five sub-groups is reasonably significant while remaining easy to manipulate. Thus the value of n, the number of articles in a sample group should desirably lie in the range 8 to 12 and preferably be 10.
  • a convenient apparatus may comprise a beam balance as specified above as well as a second weigher, preferably a two pan equal arm beam balance, for determining the lighter and heavier articles.
  • FIG. 1 is a perspective view of a weighing machine
  • FIG. 2 is a diagram illustrating the principal of this machine.
  • FIG. 3 is a graph depicting normal distribution weight spread.
  • FIGS. 1 and 2 show a simple apparatus for carrying out the invention. However reference will first be made to FIG. 3 which shows graphically what the invention sets out to do.
  • the full line curve is a conventional normal distribution curve ofweight W against numbers of articles N at any given weight.
  • the peak of this curve represents the meanweight, and in practice a filling machine will be filling to a target weight T W corresponding to this mean weight. Then, dependent on legal requirements or accepted practice, therewill be a point on thiscurve which indicates the maximum value of weight which could be marked on the pack (this might be that 97% percent of the articles are above the declared weight in some countries and in others the requirements might be more, or less stringent than this, but the principle remains much the same). This is marked on the curve MVDW.
  • nominal declared weightNDW is normally marked on the pack and the aim is to sell product as closely above that weight as is technically and legally possible.
  • MVDW is above NDW so that the legal, or practice, requirements are satisfied, however the articles are of a greater weight than is necessary and the operation is not economically at the optimum.
  • the target weight of the filling machine is shifted downwards to a new target weight TWl by an amount which brings MVDW downwards to a point where it will virtually co-incide with NDW and the whole of the normal distribution curve is shifted to the position shown dotted.
  • the present invention uses a particular form of weigh scale which for a given group of articles automatically computes the position of MVDW for that group and hence enables the target weight or the nominal declared weight to be adjusted accordingly.
  • the weighing machine has five weigh pans P1, P2, L, H and DW.
  • the linkage connecting these pans is shown in FIG. 2,'the points F in each case indicating a fixed fulcrum.
  • pans P1 and P2 are connected by a simple equal arm balance acting about Fulcrum F1 and their function is to distinguish between the heavier and the lighter article in any pair.
  • the pans H, L and DW are connected together by a more complex linkage.
  • the pan H is intended to take all the heavy articles in a sample and is located a distance A from the fulcrum F2.
  • the pan L for the lighter articles is located a distance B from fulcrum F2 on its other side.
  • an upward force due to the pan DW (for declared weight) is applied to a pivotal connection PC. This upward force is transmitted via an equal arm balance pivoted about fulcrum F3, but in an alternative arrangement the pan DW is located .the same distance C on the other side of the fulcrum F2, and directly connected without the additional equal arm balance.
  • the distances A, B and C are selected in dependence Take ten articles from the production line, place the first two on scale pans P1 and P2 to establish the heavier and the lighter, place the heavier on pan H and the lighter on pan L, repeat the sequence with the re maining articles in random pairs thus ending with five articles on each of pans H and L, and finally place weights on pan DW until the complex scale balances.
  • the weight at pan DW then indicates the maximum safe declared weight.
  • the weigh balance is establishing the relationship A E H B E L CDW where A, B and C are constants H is the sum of the heavy articles L is the sum of the light articles, and
  • DW is the maximum safe declared weight.
  • the arm ratios are 1:0.224z0. l 24 with z being equal to 1.74. If we are working to a greater degree of security where K 3 standard deviations, z is equal to 2.66 and the arm ratios are then 120.3 16:0.216.
  • a method of determining the maximum safe value of declared weight for a series of articles of nominal declaredweight comprising:
  • a weighing apparatus for determining the maximum safe value of declared weight for a series of n articles of nominal declared weight comprising a beam balance having three weigh stations effectively located at different distances from a pivot point, said distances being in the ratio 1 (z 0.5)/n (z 0.5)/n where n is the number of articles in a sample group within the series and z is a constant dependent on the tolerated difference between declared weight and mean weight of the series of articles, some of the articles being rela-- tively heavier while the others are relatively lighter, the weigh stations having moment arms (2 0.5 )/n and (z 0.5)/n supporting equal numbers of relatively lighter and relatively heavier articles, respectively, the weigh station having moment arm 1 having balance weights placed thereon until the scale balances, the amount of balance weight indicating the maximum safe declared weight.
  • a weighing apparatus which further comprises a second balance, said second balance being arranged to distinguish between lighter and heavier articles in subgroups from the sample group of articles.
  • a weighing apparatus according to claim 5 where the constant z lies between 1.5 and 3.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Basic Packing Technique (AREA)
  • Weight Measurement For Supplying Or Discharging Of Specified Amounts Of Material (AREA)
  • Sampling And Sample Adjustment (AREA)
US00393387A 1972-09-04 1973-08-31 Weight quality control determination Expired - Lifetime US3814195A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB4084272 1972-09-04

Publications (1)

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US3814195A true US3814195A (en) 1974-06-04

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US00393387A Expired - Lifetime US3814195A (en) 1972-09-04 1973-08-31 Weight quality control determination

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US (1) US3814195A (enrdf_load_stackoverflow)
CA (1) CA966514A (enrdf_load_stackoverflow)
DE (1) DE2344302A1 (enrdf_load_stackoverflow)
FR (1) FR2198128B1 (enrdf_load_stackoverflow)
NL (1) NL7311998A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050224343A1 (en) * 2004-04-08 2005-10-13 Richard Newcomb Power coupling for high-power sputtering

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2484324A (en) * 1944-08-17 1949-10-11 Thorsson Matthew Three-bucket counting scale
US2802658A (en) * 1954-06-16 1957-08-13 Swift & Co Weighing method and apparatus
US3708025A (en) * 1970-09-21 1973-01-02 Mateo Grau Hijos Sa Method and apparatus for selecting objects to be formed into groups

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2484324A (en) * 1944-08-17 1949-10-11 Thorsson Matthew Three-bucket counting scale
US2802658A (en) * 1954-06-16 1957-08-13 Swift & Co Weighing method and apparatus
US3708025A (en) * 1970-09-21 1973-01-02 Mateo Grau Hijos Sa Method and apparatus for selecting objects to be formed into groups

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050224343A1 (en) * 2004-04-08 2005-10-13 Richard Newcomb Power coupling for high-power sputtering

Also Published As

Publication number Publication date
FR2198128A1 (enrdf_load_stackoverflow) 1974-03-29
CA966514A (en) 1975-04-22
DE2344302A1 (de) 1974-03-21
NL7311998A (enrdf_load_stackoverflow) 1974-03-06
FR2198128B1 (enrdf_load_stackoverflow) 1976-10-01

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