I've found several threads about nipple clamps, but not any that appear to address this particular problem...
A couple of years ago, I bought some vibrating nipple clamps for my wife to try out. They had small sprung clips on the ends and an adjustable screw to set the minimum gap. When I first applied them (gently, and on the widest setting), my wife was intrigued by the initial sensations. However, we couldn't get the darned things to stay on for more than about a minute -- after that, her nipples would do a Houdini-style escape and pop out of the clip.
Needless to say, this was frustrating for us both. I tried undoing the screw progressively to narrow the minimum gap, but this seemed to make matters worse -- either her nipples would pop out even more eagerly due to the increased pressure, or I wouldn't be able to fit them into the clips in the first place. After quite a few repeats, the routine started to become comedic, and we both lost the mood and the will to continue.
My impression was that the clamps were simply way too small -- although I see that other LH products are similar. I don't think my wife's nipples are gigantic, but I'd expect to be able to get her whole nipple into a clamp, and that's just not going to happen. Obviously, with only part of the nipple gripped, the vibrations are likely to contribute to easing the clamp off.
Has anyone else had the same problem? Am I missing something about the way that these toys are supposed to be used? Is there a better product for us out there?
Many thanks for any thoughts!