Silicone Tube Cutter

Client Coordinators: Alan Pitstick, John Wiltshire, Jon Kuniholm
Designers: Jason Liu, Meagan Gray, and Pallavi Kansal
Supervising Professor: Larry Bohs

A device has been developed to enable individuals with disabilities to cut resilient silicone tubing into identical length bands.  These bands are designed to replace currently available rubber tension bands that fail quickly and easily on the hooks of body-powered arm prostheses.  The device allows for easy insertion of silicone tubing while ensuring proper alignment for clean and uniform cuts.  A lever enables workers to cut tubing with minimal effort, and the cut bands eject automatically into a container underneath the device, which is removable for later inspection and packaging.  This portable device enables employees with disabilities to mass-produce tension bands safely and efficiently.

The Silicone Tubing Cutter will enable workers at OE Enterprises, Inc, a vocational rehabilitation facility, to create longer-lasting tension bands for prosthetic arm-hook prehensors.  These bands can then be packaged and sold by OE.  The device creates a vocational opportunity for workers at OE, an income source for the company, and better tension bands for users of body-powered prostheses “that should make a lot of people [with prosthetic arms] happy,” according to Jon Kuniholm of the Open Prosthetics Project.

The Silicone Tube Cutter (Figure 1) is composed of a cutting device, a wood base, and a collection bin. The cutting device includes two custom-milled 5.5’’x4’’x1.25’’ blocks of aluminum.  Silicone tubing enters the device through a small square hole in the side of the top block.  This entryway guides the tubing into the device and hinders it from curving to the right or left.   It is lined with felt to reduce friction between the device and the tubing.  The top block contains a rectangular hole through which a spring-loaded plunger slides up and down as the user pushes on a lever.  Beneath the plunger in the bottom block, a standard single-edged razor blade is mounted perpendicularly to the tubing axis.  As the user depresses the lever, the plunger compresses the tubing onto the blade and cuts the tubing.

The side of the hole opposite the entryway serves as a “stop” for the tubing to ensure it is cut at ½”.  Mounted to the stop is a light-touch switch, which is connected in series with a LED, current-limiting resistor and two AA batteries.  As the user inserts the tubing, the switch depresses and the LED goes on, signaling that the tubing is fully inserted and ready to be cut.  Once the lever is depressed, the cut piece of tubing falls through a milled hole in the bottom block into a collection bin.

A lock between the top and bottom blocks prohibits access to the blade during use, while a hinge allows for OE managers to open the device and replace the blade when necessary.

The cutting device is attached to the base, a rectangular box made from red oak.  A small rectangular hole in the top surface lines up with the hole in the bottom aluminum block, allowing the cut bands to fall into the collection bin, a commercial plastic container.  A hinged door on the front of the base is locked during use so that workers cannot insert hands into the cutting area.

The lever is constructed from 2.5’ of  ¾” steel electrical conduit.  A 1.5×3.5×7.5’’ piece of wood serves as the lever fulcrum.  A key-shaped hole allows the plunger bolt to insert easily and slide as the plunger arm pivots.  An OE Enterprise manager can easily remove the lever by unscrewing the fulcrum bolt and then sliding the lever towards its fulcrum, thereby allowing access to the cutting chamber.

The tubing must be held with its natural curvature as shown in Figure 2 for the most accurate cuts.  This can be done by the user, as shown, or a reel of tubing can be mounted above the device.  Cost of materials for the Silicone Tube Cutter was approximately $160.

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