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Scale Theory

Self– indicating Pricing Scales

By February 6, 2024
In the previous weighing news, the necessity for the weighing and pricing scales and the invention of steelyard type pricing scale were described. The steelyard type pricing scale was non automatic and was therefore slow in use.

Self– indicating Pricing Scales:

It was soon followed by the Dayton automatic computing Scale with suspended pan.
The swinging pan was replaced by a goods fitting on a Roberval system. In 1907 Henry Pooley & Son Limited, by arrangement with the Dayton Computing Scale Company, successfully submitted to the British Board of Trade, a scale of the type illustrated in the figure.
One of the chief modifications to this type was the introduction of a pendulum resistant unit in place of springs, by the Toledo Scale Company of U.S.A. Figure shows the first scale of pendulum type brought to England, sold through the agency of W.& T. Avery Limited.
These cylinder type of Scales usually had a capacity of twenty pounds, with a minor division on the chart of half – an – ounce. Since the Board of Trade Regulation required, on verification, an accuracy of a subdivision, the Scale should be accurate to 1 in 1280. Great skill and extreme accuracy in manufacturing made it possible for the commercial production of reliable scales to this standard.

Industrial Self – indicating Scales

Many ideas for heavy capacity scales of the self-indicating type were tried and several of these became obsolete.

In the beautifully illustrated book “A Short History of Weighing” written by L.Sanders and published in 1947 by history employers W. & T. Avery Ltd., there is a reproduced page from a weighing machine catalogue issued by Henry & Son Ltd., in 1859 showing a spring dial platform scale in use in railway parcels office. Mr. Sanders said – and no one could speak with greater authority – that this was probably the first self-indicating platform scale used for industrial purposes. Henry Pooley constructed Hydrostatic balances as early as 1874 and some remained in use for many years.
In 1907 Henry Pooley& Son Limited, introduced their “quadrant indicator” a massively constructed pendulous lever, carrying at one end a quadrant with a specially designed chart having an inclined vernier scale enabling small subdivisions of weight to be read. In the indicator shown in the figure, the chart and window are hidden behind uprights.
An important invention, known as the Aerostat, was made by Mr. Stickig at the beginning of the 20th century. This mechanism operated on a principle which formed the basis of many dial weighing machines.

The Aerostat mechanism was applied to platform Scales and weighbridges by W. & T. Avery Limited, in 1906.
In 1924, Avery introduced a semi – self-indicating platform scale which was marked with very small subdivisions of weight. Figure shows one variation of this model, the invention of C.Mc.G.Sykes. Essentially there was a steelyard with sliding poise for balancing the major units of load and a subsidiary pendulous resistant unit which gave automatic indication of the minor divisions.
Scale Theory

Semi self – indicating counter scales

By February 6, 2024
Disadvantage of the spring scales is that with repeated use, the spring in the scale can be permanently stretched, which tends to bring less accuracy.
The cam was introduced around 1906 to enable chart graduations of equal width to be obtained. As the pendulum moves outwards, under the influence of the load, to a position of equilibrium, the indicator traverses the chart and indicates the correct weight. Figure shows a semi – self-indicating scale of cam and pendulum type with Beranger lever system.
These are based on Levers, Knife-edges & Bearing System for durability, sensitivity and consistent accuracy. The lever based Self and Semi-self indicating Counter Scales are suitable for quick and accurate weighing in retail shops and in numerous fields of industries.
S e m i – s e l f – i n d i c a t i n g c o u n t e r s c a l e s were designed to prevent the use of weights of small denomination when weighing goods in varying quantities to facilitate repetitive manual weight of a particular loading, precisely or within tolerance. Assemblies comprise one of the conventional counter scales of Roberval, inverted Roberval, Beranger or Phanzeder pattern associated with a variable resistant of the cam or eccentric pendulum, tension spring or torsion strip type. We have already seen that Roberval principle has formed the basis of many types of counter scale and for many applications, it was the most convenient form of lever system.
In one of its variations the stays were arranged above the beam, known as Imperial Scale.
In the middle of the 19th century, Joseph Beranger, a French scale maker, invented a system of levers by his name. This design was very reliable and accurate. The Beranger design permitted several variations and in which one the Phanzeder became popular in the continent of Europe.

Self-indicating counter scales

Self-indicating weighing machine means a weighing instrument in which the whole or part of the weight of the goods being weighed is indicated by a pointer moving over a scale or chart graduated in units of mass, or a graduated chart moving in relation to a fixed pointer, or a digital display, or by means of a printed record which avoids Physical or mental effort in weighing and pricing of goods.
The idea of making the scales to indicate value of the goods, as well as weight, occupied the minds of inventors in the 19th century. One of the earliest of the price indicating scales to be made on a commercial basis was the Stimpson steelyard computing scale, which made its appearance in 1897, mostly in American market. The figure shows such a scale, the steelyard carries a flat rectangular chart graduated in units of weight and with price computations.

It was soon followed by the Dayton automatic computing scale with suspended pan.
Scale Theory

Hydrostatic balances

By February 6, 2024 0 Comments
Leonardo da Vinci’s, universal genius of the 15th century notebooks contain sketches and a description of two self – indicating weighing mechanisms, one being semi – circular in form, the other triangular.

The models were constructed by the research department of W.&T. Avery Ltd working from the sketches from Leonardo ‘s notebooks, preserved in Paris.
Although Leonardo da Vinci’s sketches of these mechanisms were essentially practical in conception, no attempt seems to have been made to exploit the invention until 9th century.
A simple pendulum balance patented in 1863 consisted of a pendulum made from flat sheet brass and suspended from shackle as shown in the figure. The load was applied by a cord and ring. The circular pendulum weight formed a graduated scale at the centre. When a load was suspended from the instrument, the pendulum swung outwards to a position of balance and the pointer indicated the correct weight. These little balances were made for weighing letters and postal packages.
In chronological order, Richard Salter of George Salter & Co.Ltd.,West Bromwich is known to have been made a barrel spring balance in the year 1770. At first, a compression spring was used and later spring balances incorporated tension springs.
Augustus Siebel invented the bow spring balances in 19th century and subsequently the elliptical spring balances in partnership with H.Marriott.
The latter form of resistant and indicator used in platform scale for many years and supplied to Railway companies by Henry Pooley.
Hydrostatic balances were constructed as early as 1874 by Henry Pooley and some remained in use for many years.
The indicator consisted of a beam or lever, one end, which was connected to a conventional load carrying system of a platform scale or weighbridge as in the figure. From the other end, a counter poise was suspended dipping in a tank of water. When a load was applied on the platform scale, the counter poise was raised out of the water, losing part of its buoyancy until a position of balance was found automatically. In one version of the scale, an indicator was driven from motion of the lever by means of a chain and drum and the weight was thus read on a graduated chart.
Scale Theory

COMPOUND LEVER BALANCES

By February 6, 2024 0 Comments
Thaddeus and Erastus Fairbanks’ agents took out a British patent for a compound lever scale in 1833. However, it was declared invalid when English scale makers proved that the invention had been in use for a number of years.

In the year 1730, in the Birmingham street called Digbeth, there lived one James Ford who made steelyards. All his work was done by hand; machinery was at the time unknown in this trade. In this humble domestic workshop, the business then conducted by W.&T.Avery Limited began.
Ford died in 1761 and the business passed through the hands of James several family connections until it came under the control of William and Thomas Avery in 1818. In their hands, it began to grow from a purely local concern trading with Midland people and a few travelling merchants into a nation wide and finally world-wide organization. New types of scales were made and new markets found. In 1894, the business was formed into a Public Limited Liability Company. The Avery business in India was originally conducted through London export houses and in 1947, this organization which had been operating as branch of W.&T. Avery Limited was established as a separate Indian company under the title of The Avery Company Limited.
Platform scales were originally fitted with loose – weight steelyards and with these, the major portion of the load is balanced by loose proportional weights and a small sliding poise serves to balance and indicate the odd pounds and ounces.

No-loose weight steelyards were introduced later and fitted to platform scales and weigh bridges. In these, a major poise balances the greater part of the load such as tons and the smaller sliding poise serves to balance the remaining smaller portion of the load.

COMPOUND LEVER BALANCES

A combination of Roberval system and steelyard was used frequently for commercial weighing. Basic structure of two such weighing machines is shown in figures. In the first figure, equal arm beams are employed and in the second, unequal arms are used to obtain mechanical advantage. The systems used for the scales, so far mentioned, is for the non – self indicating scales. Non-self – indicating weighing Scales are weighing instruments for which the equilibrium position is obtained totally by the operation of the user. The progression of the weighing scales obviously didn’t stop with the non – self indicating scales.

SELF-INDICATING SCALE

A self-indicating scale is capable of balancing a load automatically and giving an indication of its weight, without the operator having to manipulate weights, proportional weights or sliding poise. These scales, in many forms and now in digital display, are indispensable to modern commerce.
The first records of the invention of the self-indicating scale were made by the universal genius of the 15th century,Leonardo da Vinci, whose paintings ” The Last Supper ” and ” Mono Lisa” are world famous. His notebooks which were compiled over a period of forty years, contain sketches and description of two self-indicating weighing mechanisms, similar in principle, one being semi-circular form and the other triangular.
Scale Theory

COMPOUND LEVER

By February 5, 2024 0 Comments
Hitherto, as we have seen in our last issue, the use of the Beam and counter scale (single lever) all of which incorporate an equal armed lever or beam, yield no mechanical advantage, loads counter balance by weights. Also the Bismar and Roman steelyard can weigh substantial loads by means of relatively small weights (resistant).

COMPOUND LEVER

A system (as in various weighing scales) of two or more levers arranged to transmit motion or force by linking an arm of each lever to an arm of the next lever in the train.
Although the discovery of the principle of lever as a means of weighing is attributed to Archimedes (287-212 BC), it is a fact that common steelyard was in use throughout the Orient and India many centuries before him which we have seen in detail under the heading Bismar and Roman steelyards. But it is believed only Archimedes defined the principle of lever mathematically.

COMPOUND -LEVER SCALES

In compound lever scales (platform scales) more levers are linked, each affording a mechanical advantage providing a more compact assembly by suitable arrangement of the levers. The Roman principle also forms the basis of steelyards fitted to platform scales.
The Turnpike Act of 1741 authorized road trustees to erect at toll gates “any crane, machine or engine, which they shall judge proper for the weighing carts wagons or other carriages” and charged them to levy toll according to weight and to apply revenue to the repair of roads.

Although this Act increased the number of cart steelyards, the inconveniences of weighing by them spurred inventors to devise some less laborious and expeditious manner of weighing.
It has been claimed by Eayre and Yeomans that they invented the platform scale, but John Wyatt constructed the first compound lever platform scale around 1741 and his first weigh bridge was erected at the Birmingham Work house. Wyatt’s genius and the enormous value of his invention were not recognized in his time.
The only scale in use in the United States at that time were the even balance and the Roman steelyard. Weighing heavy and bulky products on the steelyard was a slow and laborious operation. When an enthusiasm for growing hemp swept over Vermont, the problem became acute.
In 1824, Erastus joined Thaddeus’ lucrative business. The two brothers formed the E & T Fairbanks Company in St. Johnsbury, Vermont. Once in business together, the two brothers realized that the current weighing system yielded inaccurate results. So, Thaddeus decided to invent a new, more dependable weighing scale. Innovation found in the form of Levers. Now his scale was not only accurate, but very stable. In 1830, Thaddeus built his first real scale and applied for a patent. The new scale was a hit. There after the Fairbanks brothers manufactured many different kinds of scales, including delicate instruments for chemists and jewelers as well as huge platform scales for railroads and canal weigh locks.
  • Their agents took out a British patent in 1833. The later, however, was declared invalid when English scale makers proved that the invention had been in use for a number of years.
  • It is only fair to add that the introduction of Fairbanks’designs led to great improvements in the manufacture of weighbridges and platform scales throughout the world.
Platform scale may be portable or dormant. Platform scales include those of low capacity, frequently referred to as bench platform scales, which can be carried from one position to another, and those which are moveable.

Dormant platform scales are essentially immobile, as their name implies and, in many features of construction, they resemble weighbridges. The name weighbridges was applied to relatively high capacity dormant platform scales used for weighing wheeled traffic i.e. road vehicles and rail trucks.
Weighbridges are used all over the world, both small and large companies, as well as transport companies, weigh trucks that transport all types of cargo, from food products to metals, as well as durable consumer goods or sold.

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