Final Design

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1. Ratchet Suspension 

       This component is from the Pyramex Ridgeline Graphite Designs 4 Point Ratchet Replacement Suspension System and operates via a rack and pinion. The pinion is turned by hand using the triangular knob on the front of the device. As the pinion turns it drives the racks attached to side bands which tighten or loosen the headgear. This component is the main mechanism used to change the sizing of the headgear. The total range of the ratchet is 50mm, which allows the headset to fit 99% of head sizes. There is a layer of foam padding between the ratchet and the surface of the skin which offers greater friction and comfort. It is connected to the L-frames via a two piece push in rivet; which allows the ratchet to be easily removed from the rest of the headgear and replaced in case there's a need for a new ones.

2. L frames 

        These frames are designed to support the probe positioning mechanism. The shape is designed to go around the patient's ear and ensure that the appropriate spot on the temple is exposed. It has two slots for the velcro straps that connect the two L-frames to each other. One velcro strop goes over the top of the head, and the other sits on the back of the head right above the neck.

        The frames are made with Low Density Polyethylene (LDPE). LDPE was chosen because it meets Class 1 medical device standards and is flexible enough to conform to the patients head, but rigid enough to support the weight of the probe and connecting devices

3. Slotted Rails 

        These rails are connected to the L frames using a single bolt and can be tightening through a knob. The rails are free to slide along the bolt for transverse motion as well as rotate around the bolt in a plane parallel to the side of the head. Once the proper probe position is found, the knobe on the L-frame is tightened to secure the slotted rail in place via friction between the L-frame, slotted rail, and knob.

        The slotted rail is made of acrylic which was chosen because it is rigid does not deflect under the weight of the tip-tilt plate and probe. Acrylic also has a high coefficient of friction with the LDPE of the L-frame which means when tightened, it will not rotate about bolt in the plane parallel to the surface of the skin.

4. Tip-tilt Plate

        The probe, which sits flush with the surface of the skin, needs to be able to tilt about two axis. In order to achieve this, we needed a tip-tilt plate with three points of contact. We were able to find an exact device used in optics that satisfy all our requirements online - standa 5OM10T. This devices allows for fine tuning of the tip/tilt angle and is capable of locking into place once the most optimal position is achieved. 

        The Standa 5OM10T is made of anodized aluminum. It has a very small profile, a degree arc of 10 degrees along each axis of rotation, and multiple mounting points.It consists of two small knobs located on one side of the plate, and each knob controls the movement of one axis.

5. Attachment to tip-tilt plate

        The purpose of the probe attachment is to secure the probe to the tip-tilt plate. The Standa 5OM100A1 attachment for the stand 5OM10T tip-tilt plate was chosen because it mounts directly to the tip-tilt platte and holds the probe off to the side of the plate, minimizing the profile of the TCPH. There is one set screw which can be tightened to secure the rest of the probe.

6. Probe Pipe-Fitting

        When the probes are put into the attachment shown in 5, it does not reach the surface of the patient's head. To solve this problem, a pipe-fitting design was created. The Probe attachment insert is mounted within the hole of the 5OM100A1 and securely holds the TCD probe closer to the patient's head. The slot in the back allows the wires on the probe to go through. This component is 3D printed using PLA.

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