Proven product reduces production costs
Worm-gear definition: an endless screw engages a spur-gear with spirally disposed teeth. The screw is called a worm, and the spur-gear a worm wheel – a much diminished but very powerful motion is communicated from the worm wheel.
The worm-gear is one of the oldest gearbox designs and remains internationally one of the most widely used, as they remain an economical option to produce.
The technological advances in gearbox design and manufacture over the last 50 years is why SITI is one of the leading European suppliers.
A typical small electric motor has an output speed of 1400rpm, in almost all cases, for the motor to do something useful, the speed must be reduced. Several options exist for reducing the speed of the motor, but the most commonly used are belts and pulleys or a speed reducing gearbox. A beneficial side effect of reducing motor speed is that motor torque is increased in the same ratio. For example, if you halve the speed, the torque is doubled. Therefore, a 0.37kW motor attached to a 40:1 reduction will develop a hefty 100Nm of output torque at 35rpm (neglecting transmission efficiency).
Being able to produce substantial torque at practical speeds, at the point where it is required, is a huge advantage to machine builders. For this reason, gearmotors have largely supplanted all other methods of delivering torque to move, accelerate and position any type of load.
And this brings us to the one tremendous advantage that worm-gears have and that is the ability to prevent runback.
A worm-gear with sufficient ratio cannot be back-driven by a load on the output shaft. This inherent feature is used to improve the safety of escalators, winches and lifts. When using a worm-gear, there is no need to install a separate holdback or brake to prevent a loaded, inclined conveyor running backwards when stopped. Worm-gears are used in a wide range of tilting and turning actuators, where self-locking is a distinct advantage.
SITI worm-gears have other advantages that help them to maintain their popularity. Combined with the 60 years’ plus experience of Maud Kirk, this ensures the client is provided with the most cost and production effective product.
They provide reduction ratios up to 100:1 with a single worm and wheel, making them smaller and lighter than other gears with an equivalent ratio. They have good mechanical strength, are resistant to damage, and the output shaft is at right-angles to the input shaft. This permits the motor and gearbox to be mounted directly to the head shaft of a conveyor in various positions.
SITI manufacture the MU-Series ‘Square’ worm-gears in their fully automated factory. Incorporating multiple mounting faces, MU gearboxes can be either bolted down, torque-arm or flange mounted. The hollow output shaft, with an optional bolt-in solid shaft, caters for direct shaft mounting or chain final drive. Factory filled with synthetic oil and sealed to allow universal mounting, MU gearboxes operate smoothly and quietly. They are ideally suited for driving conveyors, mixers, rollers, etc.
Maud Kirk stocks a full range of accessory items to allow designers multiple installation choices. This versatility, together with competitive pricing, ensures that SITI worm-gears remain a popular choice for small to medium drives. Maud Kirk always takes into consideration economic conveyor component costs: they work with the client to maximise their production demands.