Breastmilk pumps are well known and are generally comprised of a hood that fits over the breast, a vacuum pump connected to the hood for generating an intermittent vacuum within the hood, and a receptacle for the expressed milk. Manually driven vacuum pumps as well as those that are driven by a motor are ordinarily used. The vacuum pumps of these devices, as a rule, intermittently generate a vacuum or negative pressure within the hood, with the hood encompassing the nipple and a substantial amount of the breast. The intermittent suction action of the pump serves to pull on the breast and thereby extract milk in an action reminiscent of suckling. The milk so extracted typically flows from the hood into a collection container, e.g., a bottle, for storage and later use. A breastpump of the foregoing type is shown in U.S. Ser. No. 07/053,055, filed May 22, 1987, now U.S. Pat. No. 4,857,051.
Apart from the purely hygienic requirements for such equipment, there are also certain technical problems to consider. One such significant problem is that varying degrees of vacuum can be generated as the milk receptacle fills, which must then be compensated for. A solution to this problem is to provide a valving mechanism which serves to regulate the negative pressure applied.