1. Field of the Invention
The present invention is in the field of accumulator devices and relates more particularly to an accumulator device which comprises a pressure vessel having an oil port at its lower end, a cap member at its upper end, a gas charging valve assembly mounted in the cap member and an interior bladder assembly, which divides the vessel into two chambers in communication respectively with the oil port and the gas charging valve assembly.
2. The Prior Art
With the progressively increasing use of hydraulic accumulator devices for energy storage and for pulsation dampening as well as other uses, increasing emphasis has been placed upon constructing such accumulators in a manner in which they may be economically manufactured and yet provide a high degree of resistance to the pressures to which they are subjected in use. Known accumulators can be manufactured by a procedure which involves forming threaded connections on the pressure vessel and on the cap member used to close one end thereof. Such devices after assembly and with the introduction between the assembled parts of appropriate O-rings or like gasketing are capable of withstanding high pressures without danger of axial separation of the cap from the pressure vessel. However, it will be readily recognized that the operation of forming the pressure vessel and the cap as by a forging operation and subsequently machining the necessary threaded connections on the noted components is an extremely costly one limiting the range of uses with which the accumulator may be economically employed.
Numerous means have been suggested for effectively uniting the cap member over the open end of the pressure vessel to effect a pressure resistant connection between such parts. Such means have included rolling steps wherein the metal of the components are deformed into an interlocking engagement. By way of example, of a means of connecting such components by rolling or spinning, reference is made to U.S. Pat. No. 4,280,533. As will be readily understood by those skilled in the metal forming art however, rolling or spinning to define sharp bends or interconnections is limited to metals of relatively small thickness and thus accumulators formed in such manner are not suited to high pressure operation. Additionally, the roll forming of metals about sharp bend lines often effects crystalization of the metals in the deformed areas with resultant weakening of the metallic structures.
A further method in common use for connecting the cap components of an accumulator to the pressure vessel component involves an assembling of the noted parts and the formation of a weld between the outer wall portion of the vessel and the downwardly directed surface of the cap. However, in high pressure operations, the weld connection particularly at its interface with the outer wall portions of the pressure vessel has been known to shear or separate with resultant leakage, and under extreme conditions, the cap may be blown clear of its connection to the pressure vessel.