Home Blog Locking Bush Positions With Torque Limiting

Locking Bush Positions With Torque Limiting

Release time : 2015-06-15 09:23:17
Locking bushes from ETP have replaced mechanical clamping elements in a critical application on PET blow-moulding machines. Connecting the lever arms that open and close the moulds, the ETP-Express bushes allow slip on the shaft if there is a stuck bottle. This avoids damage to the machine and reduces downtime. Resetting is a quick and simple process compared with the old solution of a mechanical clamping bush, which had seven screws to be torque tightened in sequence. The ETP-Express, available in the UK from Techdrives, is a self-contained bush that connects shafts to hubs without keyways. A single radial fixing screw pressurises an internal chamber and expands the walls, gripping the hub and shaft. Accurate positioning, both radially and axially, is easily performed as the screw is tightened. Once the screw reaches a travel stop, the bush is set and full torque is evenly transmitted by friction over the surfaces. Up to 1000 mountings are possible. PET (polyethylene terephtalate) is widely used in beverage containers because it is light, unbreakable, stable and tasteless. It is also 100 per cent recyclable. Blow moulding machines start with a 'preform' that is pre-heated to achieve elasticity. The preforms are transported by conveyors and feed wheels into the blow moulds. Depending on the machine type, there can be from four to 36 of these blow moulds on a rotating assembly. Materials used are mostly aluminium to reduce inertia and achieve speeds up to 72000 bottles per hour. The individual blow moulds are opened and closed by a lever arm and these arms are fixed to the actuator using the ETP-Express bush. Under normal operation, the bush acts as a backlash-free connection. Should there be a jam from a misfeed, the bush slips at a predetermined torque without damaging the actuator shaft. Once the machine operators have cleared the jam, it is only a matter of seconds to reposition the mould by loosening the single screw of the ETP-Express. Expensive downtime is minimised compared with the previous mechanical locking bush, which had seven screws to be tightened. Furthermore, the low and even surface pressures of the ETP-Express avoid shaft damage and aid a consistent slip torque. The ETP-Express is a shaft-to-hub connection that is unique in concept and construction. Standard models are available from stock for shafts of 15 to 100mm and full information is available on the Techdrives website.