Patent Application
20240307945
The present invention relates to devices that are used to put pressure on objects.
When a pressurized fluid is poured into a chamber or a thick-walled cylinder, the reaction stress inside the wall is greater towards the central side and the intensity thereof decreases towards the periphery. If the stress is uniform at maximum pressure, the cylinder will withstand greater pressure.
Two cylindrical tubes, which are interference-joined, since the smaller cylinder does not fit inside the larger one-unless a gadget is made, cause the wall to be pre-stressed outwardly and pre-compressed inwardly, being the thick cylinder unpressurized. Interference-joined cylinders resist more pressure than non-interference-joined cylinders.
Nowadays, interference-joined cylindrical tubes are made and said interference is eliminated when the larger cylinder is heated, such that it dilates or expands, and/or the smaller one is cooled, such that it contracts; in that way the interference disappears, and the tubes can be assembled or joined by assembling them as a single tube. After recovering the normal temperature, they tend to recover their dimensions and cannot recover said dimensions, thus remaining “joined by the interference” or “interference-joined.”
The interference that disappears momentarily by the effect of temperature variation is truly little, and the cylinders to be joined must have an inner diameter of the outer cylinder slightly smaller than the outer diameter of the inner cylinder. Furthermore, it is difficult to maintain the temperature differences for a few minutes to assemble them or to assemble a new cylinder into another one already assembled. This was used in the manufacture of Blakely guns more than 150 years ago.
The interference that disappears momentarily by the effect of temperature variation can be greater in order to join short sections and only once, such as a gear or a railroad wheel to an axle. But it is not possible to join a set of thin cylinders tightly together by interference achieved by temperature variations.
The first mechanism to obtain high isostatic pressure is the thick-walled cylindrical chamber, wherein the width of the wall is measured as a percentage of the cylinder diameter; obviously, the thicker it is, the more pressure it withstands. But when it becomes thicker, the greater the difference is in the reaction stress between the inner and outer edge that makes the wall of the chamber, as can be seen in
The way to obtain higher pressure than a thick-walled cylinder is the “coiled chamber”: around the axial axis of a cylinder kilometers of calculated stressed plate are joined, which create pressure up to 600 MPa, that is, two- and three-times higher pressure than a simple thick-walled chamber of 30% of the cylinder diameter.
The coiled chamber has the serious disadvantage that it does not accept reaction stress in the axial direction, such that it must be fitted with large “yokes” on the outside for external support, thus supporting the caps, which may be one at each end of the cylinder, which must be completely displaced each time a chamber is loaded or unloaded.
High Pressure Processing (HPP technology) to prepare pressure pasteurized foods, or Hot Isostatic Pressing (HIP technology) used in metallurgy to make castings or remove imperfections, is well known.
The HIP technology is not used at such high pressure, only up to 300 MPa pressure, since it is used by compressing a gas, usually argon, which is heated. Furthermore, yokes and hydraulic cylinders required by the closing mechanism of the chamber make hot work more difficult.
The technology for joining by interference by temperature was used in the execution of the Blakely cannon, since he was the first one to build cannons formed of concentric tubes with varying degrees of elasticity, wherein the inner tube has a greater elasticity as it has to withstand greater stress. The straps or rings were placed in the slightly conical red-hot tube in such a way that when they cooled, they contracted and compressed it, leaving the cannon in initial stress. This allowed Blakely to build very resistant, large caliber and light weight cannons.
Even higher pressures of 10 or 100 GPa and more are exerted—for experimentation only, in microscopic dimensions in the Diamond Anvil Cell. Thousands of basic researches have been done only, since it cannot be conducted in natural size, which would be desirable to follow with applied research in new materials such as light material, super hard and tough material, electrical materials, superconductive material, etc.
The multi-wall chamber is another way to generate high pressure, but it could be said that they are attempts of other inventions, which were made for the same purpose (see patent application CL 201902913 and patent application CL 201902988). However, a new technical solution has been found that overcomes the drawbacks of the previously mentioned applications and is based on a new joint due to isostatic-pressure interference.
The new isostatic-pressure interference joining method, which is possible to conduct, serves to assemble two or ten and more cylindrical tubes of any dimension by interference, which facilitate the manufacture of ultra-high-pressure chambers or multi-chambers.
View of A detail (left side): with no pressure between the two tubular chambers, the cylinders cannot be joined by interference.
View of B detail (right side): as the pressure in the assembly chamber increases, the internal diameter of the larger tubular chamber increases and the external diameter of the smaller tubular chamber decreases, which now allows one tubular chamber to be inserted into the other.
The invention relates to a method for joining two or more concentric cylinders (101, 102) by isostatic-pressure interference, which have certain roughness or fine grooves, allowing them not to slip once assembled.
For this purpose, two tubular chambers or auxiliary chambers must be prepared, as shown in
A second tubular chamber is built a little smaller compared to the previous one, wherein the cylinder to be joined by interference (102) may have roughness or grooves on the outside, and the smaller auxiliary cylinder (202) may have roughness or grooves inside, and they are joined with two caps (113 and 114) as in the previous case. The smaller tubular chamber does not enter into the inner cylinder of the larger tubular chamber under normal circumstances, as they interfere with each other.
The tubular chambers are successively subjected to high pressure within an assembly chamber (301) keeping the interior of each tubular chamber between the caps without pressure; such that in the larger tubular chamber the internal diameter of the smaller cylinder increases in 81, and in the smaller tubular chamber the external diameter of the larger cylinder decreases in 82 due to the increase of pressure in the assembly chamber.
If the dimensions of the tubular chambers when subjected to high pressure are such that the internal diameter of the larger tubular chamber is equal to or greater than the external diameter of the larger cylinder of the smaller tubular chamber, then pressure interference has disappeared, and they can be assembled.
If the tubular chambers are subjected to a force that forces them to displace the smaller one into the larger one, when the pressure conditions are given and the diameters are forced to vary, then the smaller tubular chamber will enter into the larger tubular chamber. It can be by gravity, or an elastic band arranged, which is forcing a tubular chamber to enter into the other when the interference disappears, and they are accommodated smoothly.
When the pressure of the assembly chamber is lowered, the tubular chambers are tightly locked, since they tend to return to their diameters. The stuck tubular chambers are removed and disassembled only leaving the two cylinders joined by interference. Then, another cylinder by interference is placed and they are joined similarly, and then another one, until a cylinder formed by several concentric cylinders is formed. Then both caps are placed on them, and a chamber joined by interference of isostatic pressure is obtained.
It shall be noted that the interference-joined cylinder is pre-stressed on the outside and pre-compressed on the inside when it is without fluid, but that the pre-compressed side changes to compressed and the stress becomes uniform as fluid under pressure enters into the same.
This cylinder withstands higher pressure than a simple thick-walled cylinder of the same material and dimensions, since when it is at maximum pressure, it makes the same effort regardless of whether it is measured or calculated at a point more central or more external to the wall, as shown in
There are alternatives to generate the new joint by isostatic pressure interference, which are variations of the tubular chambers, which are assembled with one, two or no auxiliary cylinders, caps that in some cases are circular and in others ringed.
It shall be noted that the chamber (301) does not need so much pressure to produce the joint by interference of tubes that may be to manufacture another chamber, which is intended to withstand high pressure. It is enough that the chamber (301) exerts a sufficient pressure to achieve that one of the cylinders to be joined is a thin-walled one and is at maximum effort at the time of assembly.
Alternatively, only one cylinder to be joined can be used to manufacture the tubular chamber and the other cylinder to be joined neither contracts nor expands with pressure, but the interference with the expansion of the smaller cylinder in the tubular chamber is eliminated.
In order to avoid buckling due to the external pressure of the cylinders to be joined by interference-when they are under high external pressure, suitable internal supports are installed.
By manufacturing a thick interference-joined cylinder, chambers can be easily generated—such as the one shown in
Also, it can be used as a cylinder for manufacturing barrels pre-compressed on the inside and pre-stressed on the outside; it is much better than a barrel with temperature interference; furthermore, it can be used for thin barrels of ϕ 0.5 centimeters or thick barrels of ϕ 50 centimeters.
Additionally, it can be used in a multi-chamber, where it is very advantageous to exert ultra-high pressure and it is not possible to apply the coiled chambers due to the external support yokes they have. It can be further used to produce hydrogen storage tanks manufactured by cylinders joined by isostatic pressure interference, which are better than the new coiled tanks without yokes. It is necessary to produce different models for the specific function: for pressure, for size, for temperature, etc.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1788-2021 | Jul 2021 | CL | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CL2022/050069 | 6/30/2022 | WO |
