The invention relates to a spring-loaded safety valve for gases and vapor. The valve of the foregoing type includes a valve disk, which is arranged on the valve seat, supports a deflecting collar which acts as a means for assisting lift, outwardly overlaps the cross section of the valve seat and is shaped in the manner of an inner cone.
The purpose of such means for assisting lift is, on the one hand, to increase the forces acting in the valve opening direction by means of the deflection at the disk edge so as to overcome the valve spring force which increases with the opening lift. On the other hand, the increase in force per lift unit should be as constant as possible, that is, the safety valve should have a force-lift characteristic line which is as straight as possible so that the opening pressure differential and the closing pressure differential are as small as possible.
A spring-loaded safety valve is known from DE-GM No. 1 965 020, in which the deflecting collar provided at the enlarged valve disk edge is constructed as a continuous inner cone. When this safety valve is opened the lower part of the deflecting cone is still located far below the valve seat, so that the outflowing medium at the conical flow conducting surface of the deflecting collar is deflected downward relatively powerfully opposite the inflowing direction. As the lift increases, the deflecting cone, together with the valve disk, continues to move in the valve opening direction, causing the action of the diagonally extending flow conducting surface of the deflecting collar on the outflowing medium to become weaker. Thereby the increase of force per lift unit decreases, and the force-lift characteristic line flattens. Moreover, it was recognized that, with this conical flow conducting surface at the deflecting collar, the force-lift characteristic line has a break approximately in the first third of the lift, which break acts in the direction of the force reduction. Because of this flattening and this break of the force-lift characteristic line, there is a large working pressure differential which is equal to the sum of the opening and closing pressure differentials.
Moreover, it is known from U.S. Pat. No. 2,597,057 to guide the valve disk in a stationary deflecting cylinder and to arrange a threaded adjusting ring at the valve seat. Because of the stationary lower edge of the deflecting cylinder, the degree of deflection of the outflowing medium is maintained approximately until the full valve opening position; however, this valve disk sliding guide in the deflecting cylinder is relatively costly and involves the particular risk that dirt particles will be jammed in the guide gap, thereby jeopardizing the safety function. The height of the valve outflow edge can be varied by means of the adjusting ring at the valve seat and the outflow can accordingly be adapted to the operating conditions, but an improvement of the opening pressure differential always involves a worsening of the closing pressure differential, and vice versa. Moreover, the adjusting ring can be adjusted and stopped only when the system to be secured is taken out of operation.