Case History: safety device stops vertical loads, increases worker safety. (Product Innovations).

A foundry's most important asset is its workers. Safety measures must be taken with every system and equipment to ensure against failure and possible employee injury.

In the case of casting machines and trim presses with large vertical loads (the load being the portion of the die raised up during operation cycles to provide worker access), ratchet bar systems are the standard safety measure to support the vertical loads in case of machine failure. These ratchet bar systems are installed on the equipment in case of a power outage, resulting in the failure of the hydraulic or pneumatic pump and a loss of the pressure supporting the vertical load. While the ratchet bar system is expected to support the load if failure occurs, history has proven that this safety standard has a tendency to fail.

A new option for foundry equipment with vertical loads is the Single Action Safety Catcher from Midwest Technology, Inc., Muskegon, Michigan. This safety system is a clamping device that replaces the ratchet bar system and mounts around the shafts of equipment to support vertical loads in case of equipment failure. This system has replaced the ratchet bar as the standard (DIN EN 693) for Europe's equivalent to the U.S. OSHA.

During normal equipment operation in production, hydraulic or pneumatic pressure holds the safety catcher system open so the shaft with the vertical load can move up and down. This is performed as follows.

Inside the housing of the safety system several wedge shaped clamping jaws surround the shaft. Each has a sliding surface on the face away from the shaft and friction material on the surface facing the shaft. Pressure applied to the jaw's plunger forces it upward, compressing the spring at the top of the jaw. This action separates the friction material from the shaft, which then can move freely.

When power failure occurs and the pressure in the system decreases, the safety system automatically actuates with the energy of the dropping load generating the clamping force. The first step in this process is the springs expanding to bias the wedges toward the shaft. When the friction material contacts the shaft, a braking action decelerates and then stops any falling load. The kinetic energy of the load intensifies the clamping force as it draws the wedges down to a stop. This provides a safety factor ranging between 2:1 ad 4:1.

The intensified clamping pressure means that the safety system cannot be released simply by reapplying pressure to the plunger. The shaft has to be moved upward first. Thus, the condition that caused the shaft to drop must be corrected before the system will release.

Currently, the safety system has been installed on more than 60 systems in the U.S. Installation requires only 4-6 hours of downtime for the machine and can be performed during plant shutdown periods.

Select No. 002 at www.moderncasting.com/info