Abstract: A backing diaphragm (5) in a diaphragm valve for corrosive liquids is perforated by a centrally positioned, oblong hole. As known to the art a diaphragm valve for corrosive liquids contains a thin Teflon-diaphragm in contact with the liquid, and a thicker backing diaphragm of rubber or the like serving as a cushion. Both diaphragms are in close contact and are attached to a compressor by a stud bolt which is secured in the compressor by a bayonet closure comprising a cross pin in the top end of the stud bolt which is enclosed in a recess inside the compressor. In a known manner, during fitting of a new backing diaphragm the cross pin is inserted into the recess through a slot and rotated about an angle of 90 degrees. The oblong hole facilitates exchanging the backing diaphragm only without having to withdraw the cross pin out of the bolt, which is usually firmly retained therein by rust or dirt, by pushing the cross pin through the oblong hole and inserting it into the compressor.

Abstract: A rising-handwheel diaphragm valve is provided with means serving to protect the diaphragm (3) against damage by excess closing pressure. For this purpose the valve spindle (4) is provided with external screw thread (43) along its entire top portion, and the handwheel (6) is translationally movable along the spindle on a central screw-threaded bore (65). The spindle (4) is perforated near its top by a transverse bore (44), and the handwheel (6) has a raised hub (63) crossed by two transverse grooves (64), permitting the handwheel (6) to be fixed to the spindle (4) at the desired level by means of a horizontal pin (7) engaging both with the bore (44) and one of the grooves (64). The handwheel (6) is also provided with a downwardly extending collar (62) which contacts--at the desired lowermost position of the spindle--an annular planar surface (13) on the bonnet (1) of the valve casing, thus preventing undue pressure on the diaphragm (3 ).