A gear case is a container that houses gears in a machine. Manufactured of aluminum and cast steel, such a casing is strong enough to prevent the drive gears from moving out of line with the others inside. Bearings and gears operate inside of the gear case, which is full of lubricating oil and seals to prevent the oil from leaking out of the case around the input and output shafts.
Many of the machines that contain a gear case are heavy-duty machines such as earth movers and large scale cranes. Some smaller machines found within a home or office can also contain a gear case. A microwave oven can have a gear case to house the mechanism that drives the turntable inside of the oven. A blender has a gear case that provides the different speeds at which it can operate. Most machines that utilize a motor of any kind will contain at least one gear box or case inside.
An automobile transmission is perhaps the best known type of gear case. Inside of the transmission are many inter-locking gears that are meshed together to change the power level at which the automobile will produce and operate. In the lowest gear setting, the transmission produces the most power, but it requires the engine to operate at maximum revolutions per minute (RPMs). As the transmission shifts into the highest gear, typically overdrive, the gearing allows the engine to operate at lower or reduced RPMs while propelling the vehicle at a higher speed.
Some types of gear cases utilize a chain and sprockets to deliver power to a part of the machine. In the transfer case of many four-wheel drive vehicles, a chain is used to drive the gears that sends power to the front and rear axles. The chain allows the gears to operate much quieter than an all-gear drive and also utilize fewer parts to achieve the same result as an all-gear type case.
One very simple example of a gear case that is often overlooked is the common wrist watch or clock. The housing of these instruments contains a multitude of gears and interlocking mechanisms all of which are contained within the housing or case. By utilizing brass gears as well as plastic pieces and other self-lubricating metals, these cases are allowed to operate with a minimum of lubrication inside of the case.