Aquatic Development Group (ADG), Cohoes, New York, turned to hydraulic cylinders and rod locks to maintain safety and efficient control of its movable floors in its aquatic therapy pools. The company, which is a professional design, manufacturing and construction firm serving the waterpark, resort, hotel aquarium, aquatic therapy and commercial/institutional swimming pool markets, offers a design called the AFW movable pool floor system that allows depth adjustment from deck level down to deeper water for various uses, including physically-challenged patient aquatic therapy. The system is also used routinely in pools adapted for competitive swimming, diving, water polo and other activities, where the depth adjustment is beneficial and allows more multi-purpose use of a facility.
At the touch of a button on the master control module, the pool floor is raised and lowered by a system of synchronized multiple hydraulic cylinders that work to maintain consistent floor level throughout the process. To keep the system safe and secure, ADG decided to include a mechanical locking system that would secure the cylinder rods in position, at all points of travel, especially when the floor was occupied by physical therapy patients, water aerobics participants, etc. The floor also featured a passive mechanical pulley system to maintain the floor position in the event of a catastrophic hydraulic failure.
The most recent project using this system is at Ithaca College. According to ADG Engineering Manager Rob Schiavi, “We had a four-cylinder ram system with a rebar structure that was designed so that any two diagonally opposed cylinders could malfunction without compromising the stability or safety of the floor and its occupants.” He also notes that the company had developed a special 304L stainless steel and non-skid, chemically-impervious PVC floor grating that was considerably lighter weight but somewhat less stable than conventional concrete pool flooring.
The hydraulic circuits operate on a shuttle valve system with passive engage ram failure. Eliminating the mechanical pulley system on the design results in a smoother transitioning of the pool floor level, particularly important when people are present, Schiavi notes.
In designing the hydraulic ram system and in search of an appropriate cylinder locking protection system, ADG turned to its local subcontractor, who recommended the Amlok system of hydraulic cylinder rod locks from Advanced Machine & Engineering, Rockford, Illinois. AME worked closely with its local distributor, Airline Hydraulics Corp., Bensalem, Pa., to supply this system to ADG.
AME Business Development Manager Ken Davis explains, “We saw this project as an ideal application for our hydraulic rod locks, with one particular challenge, namely, the ingestion of chlorinated pool water.” To overcome this challenge, a modification was made to the seal design and materials on the four stainless steel rod locks to be installed on the ram system built by ADG’s subcontractor. Each lock has the capacity to provide a locking force to 50,000 lb at 1500-psi release pressure.
During normal operation, the RCH series of hydraulic rod locks used on this application allow free movement of the cylinder through the lock housing, as the supplied hydraulic pressure maintains an open position on the lock. When the desired pool floor level is achieved, the hydraulic pressure is removed and the cylinder is mechanically locked into position. However, in the event of a catastrophic power loss or other hydraulic system failure, when the pressure is removed, the lock immediately clamps to retain the cylinder securely in its present position until power is restored and the lock release is again activated.
Amlok rod locks retain load on hydraulic power or pump failure
The AMLOK Hydraulic Series RCH Rod Lock has been developed to provide power-off clamping of rods and shafts. They are actuated by a spring/collet mechanism and unclamped by hydraulic pressure. These rod clamps are designed to clamp components after the motion has stopped and to hold the position securely as long as the forces do not exceed the table values.
Their mountings have been designed to apply to standard heavy-duty NFPA-style MF1 cylinders. The standard housing can be mounted to any machine structure or be custom-designed to suit your application.
The AMLOK Rod Lock consists of an alloy steel housing (special materials available on request)containing a special locking mechanism actuated by a set of disc springs. The clamp is unlocked when hydraulic pressure actuates a piston that compresses the disc springs and releases the locking device.
Since the locking is accomplished mechanically and unlocked by hydraulic pressure, loss of hydraulic pressure to the rod clamp will cause the unit to lock.
The holding force depends upon the rod diameter and the amount of hydraulic pressure available for unclamping. The AMLOK is preset at the factory to release at the specified hydraulic pressure.
AMLOK Rod Locks are designed for locking axial motions only.
When attached to cylinders, longer cylinder rods must be specified. The AMLOK Rod Lock requires a full rod diameter for the entire length of the housing.
The contact surfaces and bores to which the AMLOK is clamped must be square and concentric to each other to avoid binding of the rod or excess wear. AMLOK Rod Locks can be an integral part of the housing.
The AMLOK is designed for zero side loads. When side loads are acting on the cylinder rod, the rod must be guided sufficiently in bearings to avoid side loads on the locking mechanism. This is especially important at higher cylinder rod speeds to avoid overheating the clamping device due to excessive friction with the rod.Each AMLOK Rod Lock is tested by Advanced Machine & Engineering before shipment. These test results are available upon request for evaluation.