Fort Collins, CO--For decades, electrical manufacturers have known how to simplify large, complicated systems: Assemble wiring harnesses remotely, then plug them into big components later in the assembly process.
| Two air cylinders, stacked atop one another, operate a toggle mechanism, which opens and closes the jaws that hold the air hose.
Now, one manufacturer has found a way to apply the same thinking to pneumatic components. Value Plastics, a manufacturer of pneumatic fittings, has developed a system that enables users to assemble hoses and fittings as if they were electrical wiring harnesses.
For users, the new system could save countless manufacturing hours. By some estimates, users plug more than 100 million barbed fittings into hoses every year. Engineers from Value Plastics believe they could dramatically cut the assembly time of the overwhelming majority of those 100 million hose-and-fitting assemblies.
The company's system consists of two key parts: an assembly machine that automatically plugs barbed plastic fittings into air hoses; and a quick disconnect technique that enables users to employ straight-through fittings, which can be assembled remotely, then plugged into place later in the assembly process. The two are complementary: The machine helps assemble fittings quickly; and the straight fittings allow a machine to be used for assembly (in contrast, T-shaped, Y-shaped, or L-shaped fittings could not be placed in hoses by automated techniques).
Developed by Value Plastics engineers, the tube setting machine grabs the straight fittings from a feeding track and inserts them inside plastic tubing, which is fed by a machine operator. It consists of three main parts: an air manifold; feeding bowl and magazine; and clamping head. The air manifold employs three four-way pneumatic valves, which it uses to power three pneumatic cylinders on the machine. The cylinders operate an air ram, which pushes the parts into place, and a toggle mechanism, which closes the machine's flexible jaws while the fitting is inserted.
| The TubeSetter’s clamping head (at left) is powered by air from valves in the manifold (at right). Fittings are dropped into place through a track on the machine’s magazine (middle).
During operation, the ram pushes a pin horizontally into the fitting. Two small air cylinders, stacked vertically atop one another, push on a toggle that opens and closes the flexible jaw set. When the jaw set is rotated into its closed position by the toggle, it grabs an air hose that is fed into the machine by an operator. As it does, the ram pushes the fitting into the end of the air hose. When the operator hits the machine's on-off buttons, the jaws open, dropping the assembled hose and fitting.
The two vertically oriented air cylinders enable the clamping head to have three operating positions: one for loading the hose; one for gripping it; and another for unloading it. To accomplish that, the clamping head uses one cylinder with a quarter-inch stroke and another with a half-inch stroke. By actuating one cylinder, or another, or both, it achieves all three positions.
A printed-circuit board mounted on the manifold contains circuitry for sequencing the machine. It also handles safety by not allowing the operator to actuate the machine unless he or she has both hands on the machine's two on-off switches.
The firm's engineers say that the key--and indeed the patentable concept--is the machine's flexible jaw mechanism. The jaw enables the clamping head to hold the hose in the proper position for insertion of the fitting. As insertion takes place, the flexible jaw expands with the fitting barb. As a result, it maintains its grip on the hose and enables complete insertion of the fitting. To achieve the proper balance of stiffness and flexibility needed for insertion, engineers employed Delrin plastic in the jaws.
"It's the pneumatic equivalent of a wiring harness," says Kent Sampson, Value Plastic founder and a designer of the system.
Additional details…Contact Vicki Rainsberger, Value Plastics, 3325 Timberline Rd., Fort Collins, CO 80525; (970) 223-8306.