How the Zipper Works

How the Zipper Works

A simple description of a zipper would look something like this:

A zipper (or “zip”) is a device consisting of two rows of teeth that can be made to interlock, thus tightly linking the two rows one to the other. When the two rows of teeth are not linked, the device is said to be “open”; when they are linked, the device is said to be “closed.” Opening and closing are carried out by a small element called a “slider” placed between the two rows of teeth. The slider is moved back and forth along the rows of teeth. A Y-shaped channel inside the slider meshes (interlocks) or separates (unlocks) the opposing rows of teeth, depending on the direction the slider is moved.  The slider bends the zipper slightly to open up the space and allow the opposite teeth to slide into their places.

The principal purpose of a zipper is to join two separate pieces of material (cloth, leather, plastic, etc.) so that they act as a single piece. For example, the zipper on a sports sack, wallet, purse, etc. is used to open and close the item.

There are numerous types of zippers to achieve this purpose; however, they may broadly be divided into two fundamental categories:

• Zippers that open only at one end, such as on a suitcase, briefcase, sports bag, shoes, etc.
• Zippers that open and close at both ends, such as on a jacket, blouse, vest, professional work clothes, etc.

The two categories have many parts in common; however, zippers that open and close at both ends have a few parts that zippers that open and close at only one end do not. Here are the key parts of zippers that open and close at both ends.

1. Top tape extension. The fabric part of the zipper that extends beyond the two chains of teeth, used to affix the device to the object to be opened and closed.
2. Slider. The V-shaped part of the zipper through which the two rows of teeth pass in order for them to lock (engage) and unlock (disengage), i.e. to open and close.
3. Top stops. Two pieces affixed to the top end of the zipper prevent the slider from coming off the chain.
4. Pull tab (puller). The part of the slider the user holds to pull the slider back and forth, i.e. open and close the zipper.
5. Tape width. The width of the fabric on both sides of the zipper that attach it to clothing or other objects.
6. Chain (zipper teeth). The continuous piece formed when the two halves of the zipper mesh, i.e. when the zipper is closed.
7. Bottom stop. A device affixed to the bottom end of a zipper to prevent it from spontaneously opening.
8. Bottom tape extension. The fabric part of the zipper that extends beyond the teeth at the bottom of the chain.
9. Insertion pin. A small piece extending at the bottom of one row of teeth on an open zipper that is inserted into the bottom stop so that the two rows of teeth will join when the zipper is pulled up to close, and so that the two rows of teeth will fully separate when the zipper is down to open.
10. Retainer box (pin box). A device at the bottom of the zipper to correctly align the pin so that the open zipper can be easily and smoothly closed.
11. Reinforcement film. A strip of plastic fused to each half of the zipper to allow it to be electronically “welded” onto a garment or other item without need for laborious, time-consuming sewing or stitching.

Note: The terms “bottom” and “top” are somewhat misleading. They envision a zipper used vertically; however, a zipper can be used in any orientation, i.e. vertical, horizontal, oblique. So in general, bottom simply means the end where the pull tab is located when the device is open and top the end where the pull tab is located when the device is closed.