Mining Applications

Continuous Miner | Shuttle Car Brake | Continuous Miner Brakes | Shield Hauler Brakes

Situation
When the cutterhead on a continuous miner comes to a sudden stop or encounters a momentary jam that abruptly causes a loss of cutter speed then quite often the cutterhead gearbox is damaged. The torque shockload occurs because the motor’s rotor acts like a flywheel. Its mechanical kinetic energy winds-up the drive system until something breaks.

Problem
Many different devices and drive system designs had been tried to prevent this damaging shockload. Torque shafts designed to break to prevent gearbox damage caused significant downtime. Also, over time the torque shaft will fatigue, thus lowering the torque at which it will break. Even the fastest current overload device did not work because they sense the increase in current draw after the shockload has occurred. Rubber couplings did not work because they could not provide enough wind-up to accommodate the shockload.

MiningTorque Limiters

Solution
The TLC torque limiter was designed to eliminate the shockload by absorbing the rotor’s kinetic energy and still maintain its torque setting throughout the slippage. Its patented design made the torque setting tamper resistant and eliminated problems due to worker mis-adjustment.

Over time, the concern for safety motivated underground vehicle builders to eliminate simple caliper disc brakes in favor of totally enclosed wet brakes.

Totally enclosed brakes offer three distinct advantages to caliper disc brakes. First, the friction surface and operating mechanisms are not exposed to the environment. This reduces the maintenance problems that plague caliper disc brakes on underground vehicles. Second, they can provide significant braking force in a small package. Third, when the oil bath is circulated through a heat exchanger, a totally enclosed wet brake can have greater thermal capacity.

PT Tech has been manufacturing totally enclosed wet brakes since 1984. In most cases the equipment builder has a unique requirement that existing brakes cannot meet.

The following application stories describe PT Tech’s solution to a number of equipment builder’s unique requirements:

• Shuttle Cars
• Continuous Miners
• Shield Haulers

Shuttle Car

PT Tech’s brake is flange-mounted between the electric motor and the shuttle car’s gearbox.

Situation
Shuttle car downtime was considerable due to brake problems.

Problem
Caliper disc brakes were subject to frequent, maintenance problems due to contamination in coal mines.

Shuttle Car Brakes

Solution
Replace the dry caliper disc brake with a totally enclosed wet multiple disc brake. It is flange-mounted between an electric motor and a gearbox. The motor’s splined shaft mounts into the brake and the brake’s output shaft has a spline that fits into the gearbox.

The brake is both a foot actuated service brake and a spring-applied parking emergency brake. It has greater thermal capacity and is far less susceptible to contamination problems than the dry caliper disc brake. Also, the brakes place the vehicle in compliance with International Mining regulations.

Finally, a unique friction material wear indicator provides maintenance people with a means of knowing when service is required without having to rely on the operator’s complaints.

Situation
A domestic coal equipment builder had to replace its existing caliper disc brake with a totally enclosed wet brake in order to sell into several off-shore markets.

Problem
Many overseas markets are governed by guidelines that did not allow the use of dry caliper disc brakes on vehicles.

Continuous Miner Brakes

Solution
The existing axle fitting yoke is removed. A totally enclosed wet brake is mounted to the axle around the pinion shaft. There are different pinion shaft lengths. Three different adapter plates are available that bolt to the brake’s input hub. These adapter plates accept 8.5C, 9C, and 1810 driveshafts.

Situation
The vehicle’s weight and speed are increasing. Also, the slope on which it will operate is increasing. In order to be compliant with mine safety requirements for stopping distance, additional braking torque is needed. The existing brake’s torque capability cannot be increased. Also, there is a need on existing vehicles that brakes must be retrofittable.

Problem
The existing brake is incorporated into the transmission. It does not have enough torque to properly stop the vehicle. The transmission cannot be modified to accept a larger brake.

Solution
A totally enclosed, spring applied, hydraulically released wet brake that mounts to a bulkhead was installed for additional braking capacity. It has wing bearingstyle fitting yokes on both the input and output to accept 7C driveshafts.