Hubbell MRH User Manual

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Maintenance Instructions

MRH Motor Reel

Wiring

Motor can be wired for either 230 volt or 460 volt, 3 phase, 60 hz A.C.

Follow jumper diagrams below.

NOTE:

Wiring should be done only by qualified, licensed electrician. Failure to

follow standard safety precautions could lead to serious injury.

230 volts

BLK

GRN

BLU

View inside Motor Junction Box

BRN

YLW

REDU1

460 volts

(Y)(D)

Jumpering Diagrams

310

HOW TORQUE UNIT WORKS

Gleason series MRH reels feature torque units which work on a patented self braking hydrodynamic clutch system.

The Functions of the torque unit are:

• To provide a constant torque on the drum shaft.

• To gear the drum rotating speed to the reeling diameter of the cable.

• To brake the drum when stationary.

• To allow a controlled unreeling of the cable.

• To regulate the torque output according to the requirements of each application.

The torque unit is powered by a motor rotating at a constant speed. Normally a conventional electric squirrel cage motor is used but the unit can also be powered by an air or a hydraulic motor.

The torque of the driving motor is transmitted to the drum shaft through a hydrodynamic clutch which is combined with a worm gear reduction. The output torque is only minimally affected by the rotating speed of the input and output shafts. The output torque can be set from zero to maximum torque through a spring arrangement in the clutch.

Section View of Torque Unit

Following is a brief description of the torque unit components:

(Please refer to drawing on page 5)

The bronze crown gear (item 3) has specially machined surfaces on both sides. Freely mounted on the drum shaft (item 1), the crown gear is linked to the motor via a worm gear (item 2).

There are two friction plates (items 4 & 5), one on each side of the crown gear. They are made of steel and are fixed to the drum shaft with keys. The friction plates are also specially machined so that an oil film is created between the plates and the crown gear. The oil film allows slippage as torque is transferred from the crown gear to the friction plates. Pulling force on the cable remains constant, even with the motor running at a constant speed, and is fully adjustable.

The special machining on the clutch surfaces assures that they remain lubricated, even when clutch is not moving, eliminating the normally occurring “stick-slip” effect. Variation between dynamic and static friction remains within 3-10% depending on size of the torque unit.

Since the worm gear is irreversible, the clutch also acts as a brake when the motor is off. This provides two major advantages:

A) Electro-magnetic brake, required on conventional cable reels, is not needed. B) Braking torque is the same as reeling torque, avoiding uneven pulling force on the

cable when the motor is switched on and off.

The torque unit has an adjustable spring assembly to vary the pressure on the clutch and obtain the required output. The spring assembly consists of the rear friction plate (item 5), compressions springs (item 6), the spring holder plate (item 7) and the torque regulating nut (item 8).

The springs are placed between the rear friction plate and the spring holder which is fixed onto the drum shaft with a key, allowing it to slide along the shaft. The torque regulating nut is screwed onto the drum shaft and pushes against the spring holder plate through a series of steel ball bearings.

Torque can be regulated by placing the torque regulating key (item 10) upside down into the torque unit, preventing the regulating nut from rotating. With the regulating nut held in position, the drum can be turned manually or with the help of the cable reel motor to increase or decrease the pressure on the spring assembly thereby increasing or decreasing the torque output of the clutch. Refer to “TORQUE OUTPUT REGULATION”, page 4, for details.