Oil Shear Technology

Oil Shear Technology with Unique Fluid Recirculation System

Provides Force Control Clutches and Brake
With Increased Cycle Life, Higher Cycle Rates, and Lower Cost per Cycle.

Some Advantages of Oil shear Technology

Lower Cost per Index
Higher Cycle Rates to 300 CPM
Reduced Wear and Replacement Parts
Softer, Smoother, Quieter Engagement
Longer Life without Maintenance
Lower Cycling Inertia
No Adjustment – Ever!
Severe Duty Applications
Hazardous Duty Applications
Washdown/Marine Duty Applications
Continuous Slip – Tension/Dynos
High Thermal Capacity – Compact Size

What is Oil Shear Technology?

Oil Shear Technology involves the use and control of transmission fluid in a friction device consisting of multiple friction discs and drive plates. This friction stack can be used as a brake or a clutch.

A proprietary re-circulation system built into the hub enables fluid flow through the stack, over the contact surfaces, and out to the housing or an external cooling system. In this way, heat built up within the friction stack is carried out of the stack to be cooled, reducing the wear and degradation of the friction material.

As the stack is compressed, either by pressure (air or hydraulics) or springs, a boundary film of transmission fluid is put into a shear condition between the friction surface and drive plates. Through this shearing phenomenon of the specifically designed fluid, torque is transmitted between the two surfaces accelerating or decelerating the other part. Two things are happening. 1. Much of the work is done through the shearing of the fluid itself; therefore the heat is generated within the fluid, not the friction stack. 2. The fluid film separates the friction disc from the drive plates reducing mechanical wear of the friction material.

The transmission fluid in shear transmits torque between the two components increasing as the clamping pressure increases until mechanical lock up occurs. By cooling the friction surfaces and reducing the mechanical wear, a significant increase of thermal capacity and total cycle life is possible.

Many competitive clutches and brakes depend on friction between dry surfaces surrounded by air to transmit torque. During engagement of dry surfaces, high heat caused by slipping is difficult to dissipate quickly causing wear, glazing, and friction material degradation. This in turn causes positioning inaccuracy, limited service life, and possible safety issues.

Several other benefits are provided by Oil Shear Technology. The transmission fluid used also lubricates the bearings, splines and driver pins reducing wear on those parts for extremely long life.

And the housing itself offers even more benefit. It is a highly efficient heat exchanger pulling heat from the fluid, and dissipating to the outside. Because the transmission fluid must be contained within the brake, the housing is totally enclosed and sealed eliminating outside contaminants such as dirt, dust, chips, food, moisture or chemicals. It also seals contaminates inside, eliminating friction material dust common with many dry friction products.

Why Do Force Control Clutches and Brakes Require so Little Maintenance?

The Competition

Competitive dry friction clutches and brakes require constant disc replacement, and other maintenance depending on the design. Spring set brakes tend to need constant adjustment due to friction disc wear. Wear and heat cause the friction material to wear away as well as glaze and degrade.

Because heat is a major contributor to early failure, cooling is a major concern. Attempting to allow air through the brake for cooling means dust, dirt, moisture and chemicals can get into the unit causing corrosion, sticking linkages, friction material and other components to faster wear.

There are wet brakes on the market that are just that. The units contain fluid. The fluid helps to remove some of the heat in a totally enclosed unit. However, due to the high unit pressures between the friction disc and drive plates involved, there is no real oil shear process occurring. Therefore, wet brakes still have high wear rates, and limited heat transfer from the working part of the friction disc to the housing.

Oil Shear Technology, as incorporated in Force Control clutches and brakes, solves three of the major problems regarding clutches and brakes.

How Does Oil Shear Technology Work in Force Control Products?
Reducing Wear?

A major component of Oil Shear Technology is providing a film of transmission film between the friction material and related steel disc. In a clutch, the drive plate is rotating with the input power source (typically a motor), and the splined friction disc is connected to the output or indexing shaft. Engagement causes the output shaft to be accelerated to the input speed. In a brake, the friction discs are rotating with the output shaft and the drive plates are locked to the housing. When engaged the output shaft will be decelerated to stop.

Engagement consists of squeezing together the friction disc and drive plate. This can be accomplished through a piston actuated by pneumatic or hydraulic pressure, or springs through a pressure plate. The higher the engagement pressure, the more torque is transmitted. The Oil Shear principle consists of maintaining a fluid film between the friction disc and drive plate. As they are pressed together at differential speeds the fluid film is put in shear, transmitting torque between the two parts. During this dynamic portion of the acceleration or deceleration, the fluid film separates the two parts, virtually eliminating mechanical wear. As they come together, the film is broken and the parts mechanically lock together (static torque). This however happens at a low differential speed causing minimal wear.

How Oil Shear Technology Deals With Heat.

Clutches and brakes turn rotary motion energy into heat energy. Therefore, it is important how the heat is removed. Two different scenarios create the heat in the clutch or brake. While accelerating with a clutch, approximately half of the heat goes to rotary motion and the balance to heat in the clutch. In the case of a brake, all of the rotary motion is converted to heat in the brake.

With Oil Shear Technology, much of the heat is generated in the transmission fluid during acceleration and deceleration and the rest in the friction disc and drive plates. By regulating flow rate with the proper amount of fluid through the clutch and brake, heat can be removed from the friction area.

Where does the heat go? In a standard cycling clutch, clutch brake or brake, the internal fluid circulation system design is enough for most applications. Options such as fan cooling or water cooling can be used to remove excessive amounts of heat and extremely high cycle rates. In continuous slip applications, transmission fluid can be forced through the stack to an external forced lube cooling system.

Thermal Loading and Cooling of Clutches & Brakes

Heat or thermal loads are developed in clutches and brakes during dynamic engagement. The diagram below illustrates a typical machine cycle and identifies the portions of the cycle when heat is developed at the friction surfaces, or working surfaces of the clutch and brake.

The Bottom Line

The result of Oil Shear Technology is significantly reduced wear of the friction material, and due to the lubricating properties of the transmission fluid, extended life of the bearings, splines, and drive pins. Removing the heat greatly reduces degradation of the friction material causing glazing, and fade.

Oil Shear clutches and brakes do not require adjustment because there is minimal wear of the friction materials. The torque maintains nearly full torque through the life of the brake. This means no torque fade when that extra heavy load is on the crane, or missed position on an indexing machine.

Because the unit holds transmission fluid, it must have a totally enclosed sealed housing. This not only keeps dust, dirt, moisture and chemicals out of the clutch or brake which cause corrosion, rust, sticking parts, friction material wear, but also contains any friction material dust from escaping the unit.