The invention provides a pre-
wetting sizing mechanism. An electric heater is fixedly arranged at the bottom of a pre-
wetting tank and capable of heating water in the pre-
wetting tank and keeping the
water temperature constant so as to guarantee uniformity in
sizing ratio. Meanwhile,
yarn is threaded by coordination of an upper pressure roller, a lower pressure roller, an immersing roller and three drawing rollers to be immersed, size can permeate into the
yarn fully and beneficially during
sizing, and sizing effect is improved effectively. Rotating shafts of the upper pressure roller are fixed on two sides of the pre-wetting tank through supports at two ends, a cylinder is arranged at the tops of the supports, a
piston shaft of the cylinder is fixedly connected with the rotating shafts, the upper pressure roller moves up and down in the direction of the supports,
automatic control on the upper pressure roller is realized,
yarn feeding speed is regulated automatically, and meanwhile, daily maintenance and repair of a sizing
machine are facilitated. The pre-wetting sizing mechanism further comprises a liquid level
alarm device, when the pre-wetting tank is not full of water or the water is below warning value, water addition information is transmitted to operators through an audible and visual alarm, and the yarn is prevented from being sized non-uniformly due to insufficient immersion.