Chemical apparatus and process disinfecting – deodorizing – preser – Physical type apparatus – Apparatus for treating solid article or material with fluid...
Reexamination Certificate
2000-11-27
2002-12-10
Warden, Sr., Robert J. (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Physical type apparatus
Apparatus for treating solid article or material with fluid...
C422S297000, C422S301000, C417S403000, C092S169200, C092S171100, C220S062190, C220S589000, C220S592000
Reexamination Certificate
active
06491882
ABSTRACT:
The invention relates to a high-pressure device comprising an essentially cylindrical high-pressure vessel and external prestressing means for exerting an external pressure on the vessel.
WO 95/21690 discloses a high-pressure vessel having a cylindrical liner which is open at two ends and has been placed under radial prestress with the aid of a steel wire winding. With said high-pressure vessel the prestressing as a consequence of the steel winding is equal to the tangential stress that is generated when the high-pressure vessel is pressurised.
Pressures of between 1,000 and 15,000 bar can be generated in the known high-pressure vessel. In this context the cylindrical pressure vessel can be filled with a fluid in order to exert an isostatic pressure on, for example, foodstuffs, pharmaceuticals, cosmetic preparations and the like. By means of the high-pressure treatment under these pressures harmful microorganisms and enzymes can be killed without vitamins being damaged or the taste impaired.
As a consequence of the varying stress on the known pressure vessel, hairline cracks can be formed therein, with the result that the vessel ultimately becomes unsuitable for use. In order to provide adequate resistance to the internal pressure and to prevent the formation of hairline cracks, the known pressure vessels are of relatively heavyweight construction with multiple concentric steel walls. The removal of the relatively heavyweight pressure vessel from the hydraulic press, emptying thereof and loading with new material to be treated takes a relatively long time, with the result that the throughput of the known device is limited. Making the high-pressure vessel according to the prior art of more lightweight construction in order to be able to fill and empty this more rapidly and more easily would, in turn, lead to the use of lower pressures, as a result of which the residence time of the product in the high-pressure vessel increases.
It is therefore an aim of the present invention to provide a high-pressure device with which the high-pressure vessel can be of relatively lightweight construction whilst it can nevertheless still be operated under high pressures. A further aim of the present invention is to provide a high-pressure device with which the residence time of the products can be shortened, with which the high-pressure vessel can relatively simply and easily be placed outside the high-pressure device and can be filled and emptied easily and with which a long life throughout a large number of pressure load cycles is possible.
To this end the high-pressure device according to the present invention is characterised in that the vessel is reinforced with fibres, the prestressing means comprising a compression device for exerting an axial pressure on the high-pressure vessel. It has been found that by applying axial prestressing to the high-pressure vessel by compression in the axial direction the stress pattern over the wall of the vessel is more uniform. As a result the stress on the innermost wall section is appreciably reduced, which has beneficial effect on the life of the vessel. Furthermore, the entire wall thickness is more usefully used to obtain the desired strength, with the result that the wall can be of thinner construction or, if the wall thickness remains the same, the pressure can be increased.
Preferably, the vessel is made of a composite material comprising fibres embedded in plastic. The pressure exerted by the prestressing means can be dependent on the internal pressure in the high-pressure vessel, so that no prestressing is exerted when the vessel is not pressurised. The prestressing means can comprise a pressure element which is movable in the axial direction with respect to the cylindrical high-pressure vessel and engages on an end face of the high-pressure vessel, as well as a feed line for feeding a hydraulic fluid to the pressure element. With a relatively small number of simple modifications, such prestressing means can easily be integrated in known hydraulic installations for generating pressure in the high-pressure vessel.
The high-pressure vessel according to the present invention can comprise metal and preferably comprises a composite material made from fibres having a tensile strength of 1,000 MPa or higher, such as for example, glass fibres, carbon fibres or aramide fibres. Said fibres can have been embedded in a matrix of, for example, an epoxy resin, a polyamide or polyurethane. Preferably, the fibres are oriented essentially in the peripheral direction, so that a high tangential strength of the high-pressure vessel is obtained. Suitable high-pressure vessels made of composite materials of the abovementioned type are described in detail in European Patent Application no. 96203187.8 in the name of the Applicant. A high-pressure vessel made of composite material to which axial prestressing is applied according to the invention has a life of 300,000 cycles or more for an operating pressure of 10 Kbar.
By applying axial prestressing, the shear stress in the wall of the high-pressure vessel, in particular in a wall made of composite material, is lowered.
One embodiment of a high-pressure device according to the present invention is characterised in that the high-pressure vessel is provided close to at least one of the end faces with a reinforcing ring that thickens radially towards the outside in the axial direction. To bring the prestress in the wall as a function of the distance from the axis of the vessel to the correct value, the pressure ring is shaped such that the shear stress is reduced close to the interior of the high-pressure vessel and is increased for wall sections close to the outside of the wall. Furthermore, as a result of the use of the reinforcing ring the radial stretch close to the end faces (at the location of a possible seal) is minimised.
An advantageous embodiment of a high-pressure device according to the invention comprises a housing having a longitudinal axis and a first and a second pressure chamber located along said axis. A top end face of the high-pressure vessel is located in or close to the second pressure chamber. A piston, having a piston head located in the first pressure chamber and a piston rod connected to said piston head, is movable in the longitudinal direction via the second pressure chamber as far as into the high-pressure vessel. A pressure ring is movably accommodated around the piston rod, which pressure ring is able to engage on the top end face of the high-pressure vessel. Feeding a hydraulic fluid to the second pressure chamber causes the pressure ring to bear on the wall of the cylindrical high-pressure vessel so as to apply the axial prestressing thereto. Preferably, the fluid pressure in the second pressure chamber is dependent on the fluid pressure which is exerted on the piston, so that the prestressing is proportional to the pressure on the piston and thus to the pressure in the interior of the high-pressure vessel.
The wall of the high-pressure vessel can have been built up from several layers, for example six layers, of high-tensile fibres, the liner of the vessel being made of a superelastic material. The superelastic material separates the composite jacket from the hydraulic medium and does not itself have to cope with any stresses. The liner must be able to withstand stretching of the order of magnitude of 2%. Nickel-titanium alloys or polymers such as ABS, PE, PP or polycarbonates are suitable for this purpose.
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patent: 3775043 (1973-11-01), Johansson et al.
patent: 4152111 (1979-05-01), Larker
patent: 5288462 (1994-02-01), Carter et al.
patent: 5631029 (1997-05-01), Bewlay et al.
patent: 0117148 (1984-08-01), None
patent: 0842696 (1998-05-01), None
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patent: WO 9521690 (1995-08-01), None
International Search Report PCT/NL99/00329 Sep. 1999.
Bartels Paul Vincent
Van Den Berg Robert Willem
Van Schepdael Ludo Jean Maria Mathilde
ATO B.V.
Chorbaji Monzer R.
Handal & Morofsky
Warden, Sr. Robert J.
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