July/ August 2020

HYDRAULICS Schaeffler’s new XZU conical thrust cage needle roller bearing is used both as an articulated arm bearing in LWRs and cobots and as the main bearing support for the company’s new RTWH precision gearbox. This combination of RTWH gearbox and XZU bearing is claimed to ensure the most compact design envelope and the greatest rigidity possible in applications. The double-row conical thrust cage needle roller bearing is the culmination of 70 years’ experience in the design and manufacture of needle roller bearings. The main benefit of the bearing for customers is that it has more load-bearing rolling elements than the crossed roller bearings currently used for articulated-arm bearing supports, while maintaining the same design envelope. Customers therefore have the option of using smaller-sized bearings, thereby saving on space and weight – major benefits when it comes to downsizing. This is said to open up new opportunities and possibilities in the development of LWRs and cobots. The bearing technology spawns a constantly growing array of new applications for users. Apart from more load-bearing rolling elements, the XZU unit’s X- arrangement of needle rollers in two raceways offers support distances that, depending on installed size, increases rigidity by at least 30 per cent compared to crossed roller bearings. Furthermore, by housing the rolling elements in cage guides and having them configured in two raceways instead of just one, the XZU delivers a 20 per cent reduction in friction. For customers, this all translates into more precise movement and less overshoot on reaching the end position. Overall, applications using these bearings require fewer control processes and can operate at higher 42 HYDRAULICS & PNEUMATICS July/August 2020 www.hpmag.co.uk Battery powered rail stressing pump Enerpac has launched a new cordless hydraulic stressing pump for rail tensor and stressing applications. Claimed to be the first of its type, the Enerpac ZC-3404 stressing pump is a lithium-ion battery driven with a standalone power pack used in the aluminothermic track welding process. The Network Rail approved ZC-3404 pump is a three-stage pump, offering improved reliability and efficiency for track stressing. Compatible with other rail tensors using similar pressures, the battery powered, ZC-3404 hydraulic pump has no exhaust gases compared to petrol or diesel-powered pumps. Lightweight and ergonomic As well as reducing the environmental impact of rail stressing, it provides a significant improvement in working speeds, thereby making the production cycle in question much more efficient. RTWH precision gearbox – silk hat-type speed reducer Schaeffler offers ready-to-install, silk hat-type speed-reduction gears – or ‘speed reducers’ as they are also known – for use in robot articulated joints. By harnessing the functional principles of strain wave gearing, the RTWH combines high gear ratios – and correspondingly high torques – with relatively lightweight construction. The RTWH precision gearbox developed by Schaeffler is characterised by clearance-free operation, high positioning accuracy, and compactness. It is also very durable and therefore has a long operating life. A long operating life is a key factor in robots, which need to operate with maximum reliability and minimum downtime. Depending on their size, Schaeffler’s RTWH gearboxes can deliver reduction ratios of 50:1 to 150:1. The torques resulting from these reductions are transmitted reliably and accurately due to the gearbox’s robust construction and the integration of the highly rigid XZU conical thrust cage needle roller bearing. As a result, robots fitted with RTWH gearboxes are highly efficient and able to move through to their end positions dynamically, accurately, and without excessive overshoot. This means they are able to complete sorting, handling and assembly tasks quickly and efficiently. www.schaeffler.co.uk conditions in tunnels and underground. In addition, it is approximately 50% lighter with improved ergonomics for ease of handling, and quieter with noise level below 80dB max. Safe operation is the trademark of Enerpac hydraulic pumps. The ZC-3404 uses a pressure hold function for operator safety during operation, together with a safety key to allow the pump to be safely left unattended during breaks. Technicians in the field have contributed and advised on the pump design. For example, the pump’s pressure gauge is mounted at an angle allowing the operator to safely maintain control over the pump, by standing at the side instead of facing the front of the pump. Weighing 34.8 kg (excluding battery), the zero-emission stressing pump uses an 82-volt lithium-ion battery with quick charger. The pump’s modular construction, and exchangeable battery, ensure ease of maintenance. The Enerpac ZC-3404 hydraulic pump is Network Rail approved (Certificate of Acceptance PA05-06958). www.enerpac.com Network Rail approved Enerpac ZC-3404 cordless hydraulic stressing pump. New conical thrust cage needle roller bearing and RTWH gearbox