Fluid handling – Line condition change responsive valves – Direct response valves
Patent
1984-11-01
1986-12-30
Nilson, Robert G.
Fluid handling
Line condition change responsive valves
Direct response valves
137517, 417298, 417299, 417447, F16K 1508
Patent
active
046321454
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
This invention relates to a lifting device for the closure plate of compressor valves for regulating the quanitity conveyed, with a gripper which is movably guided in the lifting direction and is acted upon in the opening direction of the closure plate by a regulating spring with tension variable by a setting device and which acts upon the closure plate by way of lifting prongs.
2. THE PRIOR ART
The object of the lifting devices used in reciprocating compressors for regulating the quantity conveyed is to delay the closure of the suction valves so that part of the medium drawn in is forced back by the piston into the suction duct. In this connection the lifting gripper participates in the lifting movements of the closure plate. During the opening of the valve the gripper strikes the lifting stop, e.g. on the catcher, whereas during the closing movement, as soon as the closure plate strikes the valve seat, it can disengage itself therefrom and swing out for the most part freely. In this connection the mass of the gripper should not exceed a certain upper limit dependent upon the structural features of the valve, so that during the shock of opening there may be no damage to or destruction of the valve. The gripper mass, however, should not be too small, as otherwise the speed of the gripper becomes too great during the closure procedure, in which the flow forces act upon the closure plate in an accelerating manner, and this in turn results in considerable stresses, in particular a hard impact of the closure plate upon the valve seat. In difficult operating conditions it can happen that the two mass limits are only a slight distance away from one another or even overlap one another, which can lead to overstressing of the lifting device and the suction valve.
German Patent No. 923 082 discloses a lifting device with a rigid gripper on which are secured sleeves in which pins acting as lifting prongs are guided. Shock-absorbing intermediate members are provided between the said pins and the sleeves, for example cylindrical pieces of soft rubber or plastics material can be inserted, stuck or vulcanized into the sleeves. The pins can be displaced independently of one another under the action of the shocks acting upon them during the regulating procedure. The stresses upon the suction valve and the lifting device itself cannot, however, be reduced in this way. It is particularly disadvantageous, however, for the closure plate not to be guided precisely during the regulating movement, so that it can be positioned obliquely under the action of the flow forces and performs a wobbly lifting movement.
SUMMARY OF THE INVENTION
The object of the present invention is to improve the lifting device in such a way that hard knocks by the lifting prongs upon the closure plate or upon the lifting stop itself are avoided, while the advantageous parallel guidance of the closure plate is ensured as in the case of the known rigid grippers.
This object is attained according to the invention in that the gripper is divided into at least two gripper parts which are displaceable relative to one another in the lifting direction and between which at least one damping spring is interposed, and the displacement path between the two gripper parts is bounded by end stops between which the damper springs are pre-tensioned, the pre-tensioning force of the damper springs being approximately as great as or greater than the regulating force of the regulating spring required for keeping the regulated valve open. By means of this design it is possible in a simple manner to select the mass of the gripper effective in each case in such a way that an optimum movement with little stressing of the parts moved is attained as the quantity conveyed is regulated. When the valve is opened only the mass of one gripper part, which can if necessary be kept small, strikes the lifting stop directly. The mass of the other gripper part, on the other hand, is spring-mounted against the mass of the first gripper
Hoerbiger Ventilwerke Aktiengesellschaft
Nilson Robert G.
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