Closable Tape Dispenser

I don't know about everyone else in this world, but I must waste more tape than I use from cutting off the inch at the end because it's gotten dirty/hairy/unsticky somehow. This might just be because I keep my roll of tape in my purse, but I'm sure I'm not the only person in the universe who is bothered by this. I've considered keeping my roll of tape in a little plastic baggy, but that gets tedious quickly.

Anyway, I propose something be done about this minor yet nonetheless insanely annoying inconvenience. I propose a tape dispenser that can be closed in order to prevent dust/dirt/hair/etc. from causing the sticky surface to lose its adhesive quality.

I drew numerous designs for this product when I used it for a school project in my Intro. to Engineering Design course last year at school, but I appear to have either misplaced the drawings or I threw them out at some point. Since I don't feel like drawing a new set of images, I'll try to describe it the best I can.

It would look like a cylinder, with the base being about three inches in diameter (that's an estimate), and about one inch thick. In the centre would be the spinning device, which would operate not unlike the ones in your typical Scotch tape dispenser (do the ones in England look the same?).

To open the dispenser, a small portion of the dispenser would be able to be swung open on a hinge by putting your thumb on of the flat surfaces and your pointer finger opposite it on the other side, squeezing a bit, and pulling outwards. It would swing back and possibly click in place so it didn't keep falling back while someone was trying to get a piece of tape.

The jagged edge for cutting the tape was what I was most worried about. In my original design of the product, it stuck out and had the potential to cut someone. As I was typing this up, I thought of a solution to this problem. It the blade/whatever was on a very small spring, it could be pushed in by the closing of the dispenser, and then upon opening would push forward a few millimeters so that tape could be cut on it.

For changing rolls of tape, one of the surfaces could be pulled open once the getting-a-piece-of-tape opening was open, so that the empty role could be removed and replaced.

That's about it. Sorry for being incoherent. If I think of anything more, I'll add it, but I think that's all of it.