Prototype 3 of Shopping Cart Catch (DWSCA-SCC-3)

These are our attempts to prototype the different parts of Direct Wheelchair to Shopping Cart Attachment (DWSCA).  In our analysis post, we took a sample of carts found in the Albuquerque, NM area.  The two parts of the Direct Wheelchair to Shopping Cart Attachment are the wheelchair clamp (DWSCA-WC) and the shopping cart catch (DWSCA-SCC).

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It is important to understand that prototypes, appropriate or not, helps us understand the problem or possible solutions a little better.

Our previous prototypes of the DWSCA:

Prototype 1 of Wheelchair Clamp (DWSCA-WC-1)

Prototypes 2 and 3 of Wheelchair Clamp (DWSCA-WC-2-3)

Prototypes 1 and 2 of Shopping Cart Catch (DWSCA-SCC-1-2)


The DWSCA-SCC-1 was neither good for pushing nor pulling the cart – which are both necessary to navigate the shopping cart.  The DWSCA-SCC-2 required threading eye bolts into holes to secure the shopping cart which requires fine eye-hand coordination.  The DWSCA-SCC-3 uses a gravity gate-latch which allows for easy attachment and release of shopping cart as we will show.
Example of a gravity gate-latch with catch-hole indicated.

Gravity gate-latch.

A gravity gate latch we purchased from a local hardware store had a catch-hole that was large enough to fit around the rear cart bar (RCB) of all shopping carts in our sample.  However, when we physically tried to catch the RCB with the latch, the latch did not open wide enough.  Jim solved this problem by grinding off the tip of the latch mechanism.  Notice in the prototype DWSCA-SCC-3 (below), only a small portion of the tip needed to be removed.

Our modifications included grinding the tip off the latch mechanism and adding a wire from the back of the gravity gate-latch to the hole in the release arm.

DWSCA-SCC-3 (gravity gate-latch) connected to DWSCA-WC-3 (insulated U-bolt) using a piece of expanded metal.

A gravity gate-latch (DWSCA-SCC-3) is attached to in insulated U-bolt (DWSCA-WC-3) using a small piece of expanded metal which eliminates the need to drill holes for our prototype.

Gravity gate-latches uses the pull of gravity to close the latch mechanism. This works best with a vertical alignment. In our case, however, the part of the frame where the DWSCA-WC-3 is mounted is not vertical. Our original design for a release pull (yellow) also served to impart an (small) additional force to allow for easy attachment to the RCB on shopping carts.

Our release pull is a metal wire looped around the hole of the release arm with the other end attached to the back of the gate-latch. This wire was then enclosed in (yellow) heat-shrink tubing.

Let’s see how it looks on Gary’s wheelchair.

Release shopping cart catch using only thumb.

Easy release of the Shopping Cart Catch.

The (yellow) loop is approximately 8 inches long to provide just enough room for a thumb.

The insulated u-bolt used to clamp the gravity gate-latch onto the wheelchair cannot be removed without handtools. But the eitire attachment may be rotated about the frame to be less obstructive when not in use.

The combination DWSCA-SCC-3/DWSCA-WC-3 may be rotated about the frame to be less obstructive when not in use.

Handtools are required to attach and remove DWSCA-WC-3 from the wheelchair. However, when not in use, the entire attachment may be rotated about the frame to be less obstructive.

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1 Response to Prototype 3 of Shopping Cart Catch (DWSCA-SCC-3)

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