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Capcoder has adopted Torqsense from Sensor Technology into its bottle-sealing machines.

Capcoder has developed specialist capping machines that tighten bottle caps within precisely defined tolerances and log every detail of every bottle capped.

Roger Brown of Capcoder said: ’Our machines are essentially simple.

’Filled bottles are presented to a torque head, which quickly screws on a cap.

’But the devil is in the details.

’A batch size is typically 10,000 bottles, which we have to cap at about one per second.

’Every cap has to be done up to the same torque and we have to provide proof of this performance.

’Sterility has to be ensured – the machine may even be working in a high vacuum to ensure that no bacteria or other contaminants are present.

’Put all of this together and you end up with a need for a highly engineered machine,’ he added.

As the need for traceability emerged, Capcoder realised it would have to develop a standard solution that, while not identical for every machine, would be based on the same technology deployed in the same way.

Because exports are the lifeblood of such an OEM, the flexibility to meet different counties’ standards had to be designed in from the outset.

Even the largest bottle tops are not that big, so handling them at the speeds required can appear impossibly fiddly.

Torqsense from Sensor Technology met all the criteria: simplicity, robustness, high speed and wireless.

’Basically we could use TorqSense “as is” for this application; we just needed to work out mounting arrangements.

’Similarly, the associated software was ready to go after a bit of calibration and some front-end graphics,’ said Mark Ingham of Sensor Technology.

Torqsense does not need to physically contact the bottle caps or shaft of the torque head it is monitoring.

Instead sensing is achieved through a radio-frequency link.

Two tiny piezoelectric combs are attached to the shaft of the torque head, perpendicular to one another and at 45deg to the axis of the shaft.

These form half of a Wheatstone bridge circuit, which is in radio contact with the other half in the main body of the Torqsense.

Ingham continued: ’When the shaft rotates, a phenomenon known as Surface Affect Waves causes one comb to expand and the other to contract, changing their electrical resistance in proportion to the speed of rotation.

’This unbalances the bridge and generates a signal indicating the torque value,’ he said.

With the Capcoder project, software was required to do two things: run the torque up to 10kgcm within tolerances of 10 per cent and record the actual value achieved.

This secures the cap to the bottle at a level of tightness that will ensure security and sterility, yet is at a level that can be opened relatively easily by an adult.

The logged values are saved to a hard drive to provide a permanent record for traceability purposes.

Brown added: ’Diagnostic fluids are distributed widely, typically to every hospital in the country, where they may be stored for months before use.

’Tracing each bottle’s origin would be practically impossible without full records being automatically produced and saved to a central location.

’We found a solution to this complex but critical problem using an out of the box technology,’ he finished.

Sensor Technology

Sensor Technology are manufacturers of TORQSENSE Transducers, the world’s first low cost non-contact rotary torque transducers designed for OEM applications. Rotary torque measurement has always been difficult and expensive.

The patented method uses a surface acoustic wave device as a frequency dependent strain gauge and measures the change in resonant frequency caused by the applied strain in the shaft.

The signal is transmitted via an RF couple from the rotating shaft to a fixed pick-up.

By using a frequency-based device, the signal bandwidth is increased, and the problem of electronic interference common with analogue signals is eliminated. The torque sensors are designed to operate direct from a PLC or a PC.

They require minimum length of shaft, have low inertia, no physical contact between shaft and housing, wide bandwidth, high resolution and accuracy resolution to better than one part in a million, and excellent noise immunity.

The technology lends itself to design of OEM transducers for specific customer applications. Applications include automotive, manufacturing machines, condition monitoring where knowledge of torque is critical, torque control of tightening procedures, and monitoring of viscosity during mixing where consistency is required. The technology replaces existing types of rotary torque sensors by providing better performance at a lower price.

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