1,051,423. Valves. H. MANN. March 24, 1964 April 1, 19631, No. 12489/64. Heading F2V. The diaphragm 23 of a pressure regulator is adjustably loaded by a spring 52 abutting a plate 53, 54. The plate has two tapped bosses 57, 58 receiving screws 59, 60, the heads of the screws abutting shoulders 65 in bosses 64 attached to the cap 61. The bosses are provided with closures 68 and seals 69. To adjust the loading, the screws are threaded more or less into the bosses 57, 58. As shown, the diaphragm actuates valve members 151, 152 via levers 24, 25, a seal 157 being provided. Flow to the diaphragm chamber takes place via orifice 155 and when the outlet pressure exceeds the predetermined value, valve 152 is seated by upward movement of the diaphragm. Decreasing outlet pressure eventually causes valve 151 to seat, whereafter manual resetting is required. In an alternative embodiment, male threaded members are fixed to plate 53, 54 and co-operate with female threaded members that abut the cap.