Without power the brakes are engaged and thus generating torque. When a DC voltage is applied the brakes release. The new BFK brakes use multi-pole technology to achieve a doubling of torque without increasing the diameter of the brake.
Electromagnetic spring applied brakes work by the application of DC current to the brake coil or coils. The resulting electromagnetic flux attracts a steel armature plate which is pressed by coil springs onto a rotating brake disc coated with friction material. The flux pulls back the armature against the spring force, releasing the brake.
Switching off the current, or a supply failure, results in the springs pushing the armature back onto the brake disc with a torque moment. These brakes can be used statically as holding brakes, or dynamically for service and emergency duties.
The BFK468 brakes exchange the traditional single donut shaped coil for six individual coils positioned around the body. The result is an increase in magnetic flux from the increased number of coil turns. This allows operation with higher spring forces and therefore higher torques. Multi-pole technology is best suited to larger brakes and INTORQ offers four sizes.
The smallest with a body diameter of 220mm has a rated torque of 150Nm which can be increased to 300Nm for holding and emergency top duties. The largest, the size 31, has a diameter of 390mm and a maximum torque of 2,400Nm. Compared to standard spring applied brakes, this represents an increase of 100% size for size.
Brake options available include a manual release lever, external protective rubber seal, aluminium cover to give IP65 protection and a microswitch to monitor either brake status or the wear limit. Half wave and full wave rectifiers are available for DC supply with ratings up to 3A.
Whilst it is true that high torque is not the only requirement in the brake market, these new brakes add a new dimension for the machine designer. Their high torque comes with small size. This in turn means attractive prices and fast engage/release times.
