PTO clutch/brakes are primarily made up of three major sub-assemblies.

They are:

Field/rotor assembly This is the coil, backing plate and rotor. The coil provides the magnetic flux that allows the clutch to pull in. The rotor provides the input rotation and is mounted on the input shaft.

Pulley/armature assembly This includes the armature disk, springs, hub and pulley. This is the output of the clutch. In some instances, a mounting flange is used instead of a pulley.

Brake assembly This includes the brake shroud, adjustment nuts and springs. By controlling the force against this brake shroud, the stopping time in the application can be controlled.

Engagement of the armature to the rotor is caused by the magnetic attraction between the rotor and the armature. The magnetic flux is transferred from the field into the rotor and then into the armature. The slots in the rotor and the armature are called banana slots. These slots allow the flux to contact the rotor and the armature in more than just two places. (A normal magnet only has a north and a south point of attraction.) By making multiple points of flux connection, the torque can be increased in this type of clutch. When the power is cut, the armature is released and pulled back against the brake shroud via the leaf springs. As the armature drags against the brake shroud, the blade is helped to slow to meet the manufacturer's stop time requirements. The shroud is attached to the backing plate via the studs. The backing plate is connected to a portion of the machine so that it can withstand the mechanical braking force. Depending upon the inertia of the system, the leaf springs can be adjusted in thickness to create a stronger torque to help meet the stop time requirements. This unit also has the advantage of being able to be adjusted as it wears. This can be a considerable cost advantage to the end user over the life of the clutch/brake.

Simple installation

Since the majority of Ogura clutches are one piece designs that come in pre-set, there are no adjustments to make either at the mower manufacturer or with the end user.

Solid forged rotor

A one-piece solid forged rotor means no chance of internal parts separation. Our rotors also have an even wall thickness around the coil which gives optimum flux distribution, maximizing torque.

Different coil voltages available

Although 12 volt is the most common, 24 volts can also be made available. Depending upon the quantity, other specialty voltages can be made.

High temperature longer life grease

All models include our special longer life grease that has shown a significant improvement in life over other standard high temperature greases.

E-Coating

Where possible, all parts in the clutch are e-coated to give maximum corrosion protection.

High temperature epoxy coil

To help prevent failure from both vibration and outside contaminants, all coils are sealed in the coil shell with a high temperature epoxy coating.

Reduced burnishing time

Ogura uses a coating on the clutch face that significantly reduces burnishing time. This is a standard feature on all units.

Adjustable for wear

All Ogura PTO clutch/brakes in this section have the ability to be adjusted for wear. This is both a cost savings and down time savings to the end user. Since the clutch has the ability to be adjusted while it is on the machine, the end user can greatly extend the life of the clutch on the machine.

Six Spring Design

Six armature springs apply an even dynamic braking force and allow for greater overall armature movement.

Adjustable brake force

In some models, the springs can be changed to increase the brake force to help stop higher inertia blades.

Heavy duty field plate

To resist deflection or breakage due to vibration, a thick backing plate is used. Projection welding enhances the connection to the coil shell. Many models also incorporate an exit wire protector.

The drawing below shows a typical flange mounted PTO clutch/brake assembly. Although we have many designs of flange mounted PTO clutch/brakes (these were first used in the 1970's), there are very few that are still used in production today. These clutches are made so that the field is mounted directly to the engine face. The other components are then slid onto the shaft and kept on by the center bolt. (Most customers have switched to the bearing mounted style because of the ease of installation.)

A flange mounted clutch does not have a field bearing. Although this makes installation more time consuming, there is also no possibility of bearing failure in this area. This means that flange mounted clutches are ideal for installations that would remain engaged for long periods of time. If you believe you have an application that would benefit from this design, please contact us and we will work out the details with you.