How the Jaws of Life Operate

Key Insights

While driving on the interstate, you lean down to retrieve your cellphone from the passenger-side floorboard. In a split second, you accidentally veer onto the shoulder, causing your car to flip as you try to correct its path. When the vehicle finally stops, you find yourself with a broken leg, trapped under the dashboard in an overturned car. In such scenarios, rescue teams rely on a set of tools often referred to as the "Jaws of Life" to cut through the car and free you.

The phrase "Jaws of Life" encompasses various hydraulic tools, including cutters, spreaders, and rams, which are designed to pry open wrecked vehicles to rescue individuals trapped inside.

In emergency situations where every second counts, the Jaws of Life are deployed to extract victims from crashed vehicles. These tools are also instrumental in rescuing individuals from collapsed concrete and steel structures following earthquakes. This article delves into the workings of these hydraulic systems, the specific functions of each tool, and the power sources that drive them.

Simple Hydraulics

While oil is typically the go-to incompressible fluid for hydraulic systems, the Jaws of Life equipment utilizes phosphate-ester fluid. This synthetic fluid is fire-resistant and non-conductive, making it the preferred choice at crash sites over traditional oil.

In a basic hydraulic system, applying force to a piston compresses the oil, which then transfers the same force to another piston, causing it to rise.

The Jaws of Life tools are among the simplest hydraulic devices, consisting of minimal components to function effectively. A portable engine pumps pressurized hydraulic fluid into the piston cylinder via one of two hose ports in the cutter and spreader. Typically, these machines use around 1 quart of hydraulic fluid. An operator-controlled valve switch determines which port the fluid enters. When fluid flows into one port, it pushes the rod upward, opening the spreader arms or cutter blades. Toggling the switch retracts the rod, closing the arms or blades.

In the following sections, we will examine the various tools commonly known as the "Jaws of Life" in greater detail.

Spreaders

Spreaders and cutters are the two tools most commonly associated with the Jaws of Life, often featured in news reports. These powerful devices can dismantle vehicles with ease, akin to slicing through a tin can. The spreader is designed to pry apart structural pieces or create openings by tearing into a vehicle's side. The cutter, as its name implies, slices through vehicles like oversized bolt cutters. Both tools operate on similar principles, and some Jaws of Life models integrate the cutter and spreader into a single unit.

A spreader features pincer-like arms made of aluminum alloy, with heat-treated steel tips for enhanced strength, enabling it to penetrate vehicles or buildings effectively. Spreaders come in various sizes, each with unique specifications for spreading force and the extent of space they can create. For instance, the ML-32 Hurst Jaws of Life spreader offers:

Other spreaders may offer varying levels of spreading and pulling force. The ML-32 spreader's body is constructed from aluminum alloy, while its piston and piston rod are made of forged alloy steel. When the portable engine is activated, hydraulic fluid flows through hoses into the machine's hydraulic pump. A typical power unit might include a 5-horsepower gasoline engine operating at 5,000 psi, though pressure levels vary. Such an engine can run for approximately 45 minutes to an hour on about 0.5 gallons (2 liters) of gas.

To open the spreader's arms, the operator adjusts a valve switch, directing hydraulic fluid through one hose into the cylinder. This action pushes the piston and rod upward. The rod is connected to linkages that, in turn, are attached to the spreader's arms. As the rod rises, the linkages rotate, causing the arms to open. To close the arms, the operator reverses the valve, allowing hydraulic fluid to flow through a second hose.

To operate the spreader, a rescue worker places the closed arms into a gap in the vehicle or structure, such as a door frame. The spreader can also clamp onto a structure, crushing any material caught between its arms.

As we'll explore in the next section, cutters function similarly to spreaders in their operation.

Cutters and Rams

Similar to spreaders, cutters feature a mouth that opens and closes. However, cutters function more like powerful jaws that crush through metal and other vehicle materials. If you've witnessed this tool in action, you know it can sever a car-door post as easily as snapping a twig. As pressure is applied, the cutters slice through the material effortlessly.

Cutters are typically constructed with an aluminum-alloy body and heat-treated, forged steel blades. The piston and piston rod are often made from heat-treated alloy steel. These tools are designed to cut or shear through materials like sheet metal and plastic, primarily used to dismantle vehicles and rescue trapped passengers. Like spreaders, they can be powered by gasoline engines, as well as electrically, pneumatically, or hydraulically.

Instead of arms, cutters have curved, claw-like extensions that taper to a point. Similar to spreaders, hydraulic fluid flows into a cylinder, exerting pressure on a piston. Depending on the direction of the force, the claws either open or close. When the piston rod rises, the claws open. As it lowers, the claws clamp together, cutting through structures like car roofs.

Cutters are available in various sizes. For example, the Hurst Jaws of Life ML-40 model offers the operator:

If you're familiar with how spreaders and cutters work, the ram will seem as simple as a pair of scissors (assuming scissors had hydraulics). The ram is the most straightforward hydraulic system, relying on hydraulic fluid to move a piston within a cylinder, extending or retracting the piston rod. Similar mechanisms are used in heavy machinery, such as backhoe loaders, to control boom arms.

The ram's primary function is to separate sections of a vehicle or structure. For example, a rescue worker can position the ram on a door frame and extend the piston to lift the dashboard, creating space to extract a crash victim.

Hydraulics are integral to many machines, but none are as crucial as the "Jaws of Life." These tools have saved countless lives in situations where every second counts, often making the difference between life and death.