Dispensing assembly with a variable-volume compression chamber and with a diaphragm

Assembly for dispensing a liquid to pasty product, which includes a container (1, 8, 101) holding the product, a dispensing head (20, 120) having a dispensing channel (21), a flexible diaphragm (30) possessing a part in the form of a dome (32) which defines, in the dispensing head (20, 120), a variable-volume compression chamber (50) in communication with the container (1, 8, 101), an inlet valve (133) being placed in this communication and allowing the product to pass only from the container (1, 8, 101) to the compression chamber (50), the said compression chamber (50), the inlet valve (33) and a dispensing valve constituting a pump for dispensing product, the said flexible diaphragm (30) being held against the dispensing head (20, 120) by a fixing element consisting of a ring (40) possessing an opening (42) from which the compression dome (32) of the flexible diaphragm (30) emerges, characterized in that the ring (40) bears an annular projection (41) surrounding the said opening (42), the dispensing head (20, 120) being provided with an annular groove (25) receiving an annular groove (34) which the flexible diaphragm (30) possesses and which surrounds the compression dome (32) of the flexible diaphragm (30), the annular projection (41) of the ring (40) being inserted into the annular groove (34) of the flexible diaphragm (30).