1. Field of the Invention
The invention relates to a closure for an opening in the housing or cover of a piston pump or the like, in particular a high-pressure fluid pump, and especially a closure for a valve housing, the closure having an insertable inner cover, a loadable and relaxable pressure-applying member for the said cover, a supporting cover which can be screwed into a threaded portion of a housing or cover part, and a loading device for the pressure-applying member.
2. Description of the Prior Art
In a known closure of this kind (German Patent Specification No. 10 72 031 corresponding to British Patent Specification No. 775314), a piston is provided in the supporting cover to form a pressure-applying member, and this piston can be loaded by a hydraulic pressure medium at the end that faces away from the inner cover. After the required final pressure is reached, a pressure screw in the supporting cover is screwed against the upper end of the piston so that this can also be held pressed against the inner cover when the pressure medium is relaxed.
Because of the purposes for which they are intended, the openings that have to be closed off in housing parts or in the cover of a piston or plunger pump are often of considerable size. They must, for example, permit a valve to be changed. At the same time the closure must be capable of withstanding the operating pressure, which, in some instances, is an alternating load. In the case of closure comprising screwed-together parts, there arises the danger of the screwed connections loosening in the course of time during operations. If the connection is not retightened in time, the threads may become flattened and the destruction of individual components may even occur.