The management team at confectionery manufacturer Joseph Dobson embarked upon a programme of measures to improve and automate selected elements of their operation. The areas for improvement were chosen on the premise that they must not compromise the heart of their traditional boiled sweet making process.

Customer requirements

All of their improvement measures were targeted towards three key objectives: better hygiene, improved health and safety and labour saving. For example, sugar for the steam pan was manually weighed in to food grade buckets, lifted shoulder high and tipped in to the steam pan – an operation needing elimination with regard to all three key objectives. It is in this steam pan, a pressure vessel mounted on load cells, that the base ingredients of sugar, glucose and water are weighed, mixed and pre-heated before being transferred to traditional open pans where the resultant mass is boiled to perfection ready to be mixed with colouring and flavourings.

Spiroflow solutions

A ‘Spiroflow’ Flexible Screw Conveyor was successfully used to satisfy this application. Initially the conveyor was approximately two and a half times the length it is now and included three bends. This is not recommended! One continuous curve is the norm. Nevertheless, the conveyor operated very satisfactorily this way for 6 years before requiring a new spiral.At the time of replacing the spiral it was decided that the ‘Spiroflow’ Conveyor should be shortened, so as to eliminate the unwanted bends. We were also asked to provide a new sack tip hopper for use within the boiling room itself. The resultant conveyor and sack tip hopper give incredibly reliable feed rates over a given time.

The load cell mounted steam pan requires a preset quantity of sugar. As the sugar, glucose and water are all added to the steam pan simultaneously, the load cells can only check that the total weight is within tolerance. To ensure that the ratio of oil flavourings, essential oils and colour elements do not exceed their legal limits, the sugar content must never be less than the preset quantity but, too much more has an adverse effect on quality.

In the application at Dobson’s, the conveyor is operating as a reliable, accurate and highly repeatable volumetric feeder. It is delivering sugar from a sack tip hopper to the steam pan some 3 metres away. For traceability and record purposes, the performance of the ‘Spiroflow’ Conveyor is checked and recorded daily. The results show that over a running time of 9.4 minutes it consistently delivers the required set weight. Dobson’s make at least 42 ‘boilings’ during an 8 hour shift. As Managing Director, Stephen Walshaw comments, “We are ecstatic about the accuracy. Spiroflow are brilliant to deal with. They give us all the support we need quickly and efficiently”.

The 20 employees at Joseph Dobson & Sons Ltd are currently producing in excess of 2 million boiled sweets a week. Accordingly, the accuracy and reliability of the Spiroflow Flexible Screw Conveyor is crucial to the achievement of output. Each boiling is poured on to a temperature controlled confectionery table. Skilled operatives then mix and continuously fold the boiling to homogenously blend in the flavourings, essences, medicinal and colour elements which are added a this point to produce that range of ‘Yorkshire Mixtures’, ‘Humbugs’, Pear Drops’, ‘Voice Tablets’ and ‘Butter Mintoes’ for which Joseph Dobson are renowned throughout the world. The boiling is then shaped and die-cut into individual sweets ready for packaging.