Posted to News on 2nd Mar 2009, 13:41
The Matrix Varistop variable torque brake comprehensively addresses the requirements of truck designers, who need trucks to get from point to point, fast, and with as small a turning circle as possible. These requirements are often complicated by the weight of the load carried by the truck and how high the load is suspended in the air: for example, the heavier the load and the higher it is, then the more unstable the truck will be, as its centre of gravity is higher. As a result, truck acceleration and deceleration must be reduced accordingly.
Thanks to variable torque braking, where the torque change is stepless, the Matrix Varistop effectively addresses this problem. The change in current to produce the torque can be generated from electronics in the truck and varied according to the magnitude of the load and the height at which it is being carried. This enables the truck to be braked from speed to rest as quickly as possible without becoming unstable.
To achieve optimum braking, the Matrix Varistop variable torque brake (the 51PMB range) can be used on the traction motor or the load wheels of fork trucks. With no DC voltage applied, permanent magnets in the Varistop generate a magnetic field, which attracts the brake armature through a multi-disc plate pack and creates 50 per cent of the brake's rated torque. In this mode the brake is a holding brake.
To disengage the brake, a DC current is applied to the brake coil in the correct polarity, and the current is increased to generate a magnetic field, which opposes the magnetic field from the permanent magnets. This reduces the clamp force at the friction surfaces and thus the torque generated by the brake. By continuing to increase the current, a point is reached when the two magnetic fields balance each other, resulting in zero force, thus zero torque. This is the brake state when the truck is in motion.
By continuing to increase the current, the brake again generates an electromagnetic field and a clamp force at the friction surfaces, generating a torque and acting now as a service brake. This torque can be increased, steplessly, to the rated torque (twice the holding torque generated by the permanent magnets), by continuing to increase to the full rated voltage and current.
About Matrix, a member of the Altra Group
In the forklift truck market, Matrix focuses on battery-powered, electric motor-driven trucks for the industrial and warehouse markets. The company supplies to forklift truck manufacturers worldwide, offering very strong design and development support to customers, from engineers with many years of FLT application experience and knowledge. This expertise, combined with ongoing research and the introduction of rare-earth magnets, ensures that the overall dimensions of Matrix brakes are kept as compact as possible.
