Hydraulic motor inside

Conditions are even worse with conveyors driven by electric motors. An electric motor of equal power rating is several times the size and weight of a hydraulic motor. Plus, an electric motor needs a gearbox to convert its high-speed rotation to the speed of the conveyor. The gearbox adds even more size and weight to the conveyor. Then, of course, electrical lines feeding the motor, and the motor itself, pose a potential risk from electric shock.

No shell game

To engineers at Tech-Roll Inc., Blaine, Wash., it just made sense to put the hydraulic motor inside the conveyor drive pulley. Doing so takes advantage of otherwise unused space inside the pulley and protects the motor from the elements and physical damage. This is especially important for conveyors used in food processing applications, where components must be shielded from caustic washdown solution. The pulley also acts as an enclosure to prevent any incidental fluid leaks from contaminating conveyed products or dripping on the floor. As a precaution, the Tech-Roll comes with a small drain hose to route any incidental leaking fluid away from sensitive areas.

As with any hydraulic motor, the pulley can operate in wet atmospheres where electrical power would pose a hazard. The motor also produces full torque at startup and at all drive speeds. Speed can be easily controlled using standard hydraulic valves.

The Tech-Roll consists of two main parts: a cylindrical shell and a modified hydraulic motor. The shell is closed at one end and fitted with a pillow block bearing. The other end is open and has the hydraulic motor rigidly mounted to a shaft and an end plate with a bearing assembly. The end plate turns around the shaft. The motor is inserted into the open end of the shell, and the motor’s splined shaft fits into a fixed flange inside the shell. The end plate with the bearing assembly closes the open end of the shell.

The shell turns around the motor-mount shaft, which is fixed relative to the rotation of the shell. Hydraulic fluid enters and exits the motor through galleries in the shaft. To simplify installation, the fixed shaft is supplied with a manifold housed in a standard flange or pillow block bearing housing.

The hydraulic motor is factory-aligned inside the shell, which ensures long life of the motor by eliminating side load that could occur from poor installation practices that can occur with conventional drives. The weight of the Tech-Roll is centered within the conveyor frame, eliminating distorted structures resulting from heavy side loads. And other than the roller itself, the Tech-Roll has no external moving parts, so safety guards and enclosures do not have to be installed and maintained.

Many advantages of hydraulics

Hydraulic motors offer additional advantages inherent to their operation. Unlike electric motors, hydraulic motors do not give off substantial heat, which is especially important for conveyors operating in temperature-controlled environments. Hydraulic motors do not need breakers or other overload protection because excessive load torque simply stalls the motor. And because much of an electric motor’s noise is generated by its cooling fan, hydraulic motors also run quieter  than their electric counterparts.

The Tech-Roll is available in three versions. The standard unit comes in five sizes, with pulley diameters from 4½ to 10½ in. and motors sized 5 to 24 in.³/rev. The smallest is the mini unit, which has a 2.8-in. diameter pulley driven by a 3 in.³/rev geroller motor. Tech-Roll’s heavy-duty unit comes in 8½, 10½, and 12½-in. diameters powered by a geroller motor displacing up to 58½ in./rev. The mini unit uses a Sauer-Danfoss 3 OMM50 motor, whereas the standard and heavy-duty units use a Parker Hannifin TE or TG series motor, depending on size.

Tech-Rolls also have an electronic speed control option. An internal Hall-effect sensor and a 30-magnet disc provide an accurate electronic feedback signal to a control that regulates  flow to the motor through a proportional valve. This allows the Tech-Roll to maintain a constant speed regardless of starts and stops of other conveyors on line. And because the motor can be repeatedly stopped and started without heat buildup, this option allows using the Tech-Roll for jogging and indexing. The electronic control can be tied into a central computer for total line speed readout and control. The proportional valve and control use a 12 Vdc signal, which avoids the risk of electric shock.

For more information about the Tech-Roll, visit www.tech-roll.com.