Getting to grips with O-ring application

A new six-finger O-ring assembly gripper from Techno-Sommer Automatic features a clever design.

A new six-finger O-ring assembly gripper from Techno-Sommer Automatic features a clever design.

This compact unit picks up the O-rings, automatically expands them to slip over a shaft, then ejects them into the groove machined into the shaft.

Two pistons, pneumatically driven independently of each other, actuate the gripper motions.

Operating air pressure for the assembly is 4 to 10bar.

With the gripper positioned so that its six spring-loaded pickup pins fit inside a relaxed O-ring, pressure is applied to the first piston.

This piston's stroke presses the pins outward to stretch the O-ring and hold it in a hexagonal shape.

This stroke can be adjusted precisely using an external scale ring to make the hexagon's size large enough to slide over the shaft where the O-ring will be installed.

With the O-ring expanded, the gripper moves to position the ring around the shaft.

When located properly, compressed air is supplied to the second piston, driving the gripper's ejector jaws forward to push the O-ring gently off the pickup pins and into its groove.

When air pressure exhausts, pre-tensioned springs retract both pistons, and the reset gripper is ready to begin the next cycle.

The pickup pins and ejector jaws can be machined to suit specific applications: the L-shaped pins also can be rotated 180 degrees to deal with smaller O-rings.

Standard pin sizes handle O-rings in a diameter range from 4 to 60mm.

Optional sensing is accomplished with two proximity switches which attach to the sides of the gripper.

Pins located under the jaws actuate these sensors.

The units six finger design ensures that the O-ring is stretched to a minimum during the installation procedure.

A free DXF CAD file drawing of this gripper is available for download from the company's website.

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