Couplings in medical technology

Nowadays, automated systems and procedures are increasingly used in medical diagnostics. Here, it is not only a matter of the greatest possible hygiene and cleanliness, but also of precision and positioning accuracy. The demands on the drive technology are correspondingly high. For the automated production of systems for in vitro diagnostics (IVD), R+W Antriebselemente GmbH has developed coupling solutions in “Hygienic Design”.

In medical diagnostics, the analysis of blood, tissue, or other samples provides important information about the state of health, for a diagnosis or the best possible therapy. Even from a small drop of blood, doctors or even patients themselves can gain crucial insights for active health management or, if necessary, the right treatment.

Automation of in vitro diagnostic devices improves and accelerates diagnostics and monitoring of drug therapies. Early and accurate diagnosis can help develop individualized and tailored treatment methods. In the best case, it can even prevent the outbreak of a disease.

In many diagnostic systems in laboratories, clinics, doctors’ offices or even in the self-monitoring of patients, circuit boards are used that are manufactured in a fully automated production process in so-called climatic chambers. In addition to the highest demands on hygiene, the manufacturing process requires extreme positioning accuracy with high dynamics in the drives. The components must be compact and have a low weight.

R+W couplings for fully automatic blank handling

For fully automatic blank handling, R+W Antriebselemente GmbH has developed a coupling solution that ensures maximum precision. The customer, a pharmaceutical company and solution provider for laboratory automation, required couplings for the fully automated production of blanks that are vaporized with substrate in the climatic chamber.

The climatic chamber operates fully automatically in a temperature range between 10 and 125 degrees Celsius, at a humidity of up to 98 percent. “Here, three different coupling types from R+W were used at the same time at crucial points,” explains Bernhard Bremauer, Key Account Manager at R+W. “Two requirements were paramount in the application: the couplings had to meet high hygienic standards, and they had to provide high precision and positioning accuracy for the drives.”

The following couplings are installed in the climatic chamber:

ZAE cardan shaft with split clamping hub and metal bellows made of highly elastic stainless steel

The ZAE is a cardan shaft with a split clamping hub for a torque transmission of 10 to 800 Newton meters, depending on the series. A Series 10 shaft was used in the climatic chamber. It covers a temperature range between -30 and +100 degrees Celsius and is absolutely backlash-free due to the friction-locked clamp connection. By default, it is made of aluminum. In this case, due to strict hygiene requirements, the cardan shaft with the metal bellows (welded) was made of material 1.4404, a stainless, austenitic chromium-nickel-molybdenum steel with a low carbon content. The material 1.4404 is an austenitic chromium-nickel-molybdenum steel with good corrosion resistance to acids and chlorine-containing media. Its main application is in the food and chemical industries.

Bernhard Bremauer explains other advantages of the ZAE cardan shaft: “The special cardan internal support absorbs the weight of the intermediate tube, which in this case is also made of stainless steel, so there is no additional radial load on the input and output shafts. In this design, the cardan shaft is mounted without disassembly via split hubs in a half-shell design.”

Metal bellows coupling BKH with split clamping hub

High-precision metal bellows couplings are used wherever positioning accuracy is required. This also played an important role in the actual application in the climatic chamber. Backlash-free, torsionally stiff metal bellows couplings guarantee exact positioning of the drive train and can be used in highly dynamic applications in a finely balanced design for very high speeds, depending on the model. They are suitable for direct drives. The metal bellows is made of stainless steel and is the core of the coupling. It compensates for lateral, axial and angular shaft misalignments with low restoring forces. Due to the high hygiene requirements in the climatic chamber, the connection between the metal bellows and the hub is welded in this case.

Compact and vibration-damping: elastomer coupling with clamping hub EKL

To dampen the vibrations that occur with dynamic drives, backlash-free, vibration-damping SERVOMAX® elastomer couplings from R+W were used in the feed module of the climatic chamber. They bring the circuit boards into position and must therefore also work with high precision. Elastomer couplings are flexible shaft couplings and transmit torques without backlash. In addition to compensating for lateral, axial and angular shaft misalignment, they can vary the stiffness and damping behavior via different degrees of hardness of the elastomer insert.

Due to the versatile properties of the SERVOMAX® elastomer coupling, it was used as a compact version with clamping hub in fully automatic blank handling. “With an elastomer insert in Shore hardness 64 D, it offers an optimal combination of torsional stiffness and vibration damping,” Bremauer explains. It is characterized by zero backlash, compensation of misalignment and excellent hysteresis properties. Hysteresis means that the elastomer insert springs back to its original state linearly and within a very short time, thus ensuring smooth running. “We are pleased that we can optimize the devices with our components and thus contribute to improving diagnostics,” Bremauer is pleased to say. “So we’ve sort of made the connection between propulsion technology and healthcare.”