How to manage fluids and dosing in vending machines

New developments in coffee machines require expert component design for effective fluid management, says Daniela Krahn of Bürkert Fluid Control Systems.

Coffee and other hot drink vending machines fall into two main categories - bulk hopper storage or individual pod dispensing, and designers are faced with many different challenges in each category. The coffee alone can come in beans, granules or liquid, combined with milk, chocolate and water, our taste for coffee on demand has complicated vending machine design considerably.

For the purposes of this illustration, we'll concentrate on the larger, bulk material dispensing machines, but the design principles also apply to a wide range of similar dispensing scenarios.

Mixing it up
The basic operation of this type of vending machine would appear straightforward. Depending on the type of hot drink selected, hot water from the heater tank is fed via solenoid operated dispensing valves to the appropriate mixing bowl or brewer unit container. The ingredients for the selected drink are measured and dispensed by similar solenoid valves and then mixed with the water in exact quantities before being directed to the dispenser head. However, the detail in getting to this point is far from simple.

The process starts with the coffee machine designer creating the process flow through the machine and generating specifications for the suppliers of the individual components. However, the flow process is not just for the end product, it must also cover cleaning procedures and general maintenance. When looking at the intricate detail of the processes required to produce a high quality product to exacting client standards, the designers must consider a range of factors.

The variety of ingredients used in the machines and their specific temperatures during operation is one such example. The solenoid valves must be resistant to all of the proposed media. This especially applies to water, the quality of which varies considerably worldwide and is often underestimated. Various degrees of hardness and calcification and the isolated occurrence of chlorides can stress the components. The solenoid valve materials and material combinations have to be perfectly designed to meet the various requirements on-site and ensure the required corrosion resistance, a high reliability and therefore a long service life.

Making it last
Each task that is expected of the valve components must be precise, accurate and repeatable, whilst, at the same time, meeting the required standards for public health. Bürkert solenoid valves for example are designed to ensure they have the required chemical resistance to withstand the cleaning and sterilisation cycles, while still being able to complete in excess of 3 million operations without intervention.

It is worth noting that the valves can be connected together into maintenance friendly modules. The single valves can now be easily connected and extended as required so there are no set design limits for the manifold. This reduces assembly times and therefore the manufacturer's production costs. The ability to build a valve combination block also minimises potential leakage sites. All elements, such as connectors, screw joints or tubes, are no longer required between the single valves meaningless connection points, which always represent a leakage danger, reducing possible sources of faults in the system.

Keeping it clean
The majority of larger drinks dispensing equipment is required to operate unattended for long periods of time and machine maintenance kept to a minimum. This has been helped by the use of CIP (clean-in-place) and SIP (sterilisation-in-place) technology, where designers are able to introduce a cleaning cycle into the machine programming and thereby reduce the time required for on-site maintenance. This has developed into state-of-the-art technology in itself and is now required in order to meet current hygiene standards.

Valves produced by Bürkert for industrial applications are frequently recommended for vending machine applications, they use high grade, premium materials, to offer the highest chemical resistance possible. They guarantee long-term, high-quality performance with significantly decreased maintenance costs.

Recommended performance specification for valve modules used in this application are: Operating pressures up to 10bar, fluid temperature of 0 to 180 degrees C, ambient temperature of 0 to + 55 degrees C, nominal diameter range from 2-4mm, connection G1/4, with stainless steel internal parts, available in a range of operating voltages.

Machines are getting smaller
Another major trend, as with most modern products, is to reduce the overall size of these machines, which requires the internal components to become more compact or have the ability to perform multiple tasks. The ability to build valve blocks instead of separate valves connected by tubes reduces the piping requirement to an absolute minimum.

The space requirement decreases and the construction becomes more compact. This simultaneously increases flexibility as additional functions are able to be integrated in the coffee machine. A further positive: The user can reduce their parts inventories both in the factory and in service.

Finally, the humble solenoid valve is looking to become more integrated into the machine of the future. Valves are becoming intelligent components within the system and able to communicate their service intervals as well as individual cycle information to the central processor. This can all help in pushing the design boundaries and surpassing client expectations.

Daniela Krahn is Segment Manager for Micro at Bürkert Fluid Control Systems, and also an expert on miniature valves for dispensing and vending applications.

Bürkert Fluid Control Systems is one of the leading manufacturers of control and measuring systems for fluids and gases. The products have a wide variety of applications and are used by breweries and laboratories as well as in medical engineering and space technology. The company employs over 2,200 people and has a comprehensive network of branches in 35 countries world-wide.

For further information please email Burkert Fluid Control Systems

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N.B. The information contained in this entry is provided by Burkert Fluid Control Systems, and does not necessarily reflect the views and opinions of the publisher.

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