Patent Application
20230321743
Manufacturing processes often require joining separate components such that a fixed spatial relationship is maintained between the components after joining. When the components to be joined are made of metal, such a process may include one or more high temperature steps during which brazing or soldering occurs.
During both brazing and soldering, metal components are brought in close proximity to one another, and a soldering or a brazing material is placed between or adjacent to joining surfaces located on each of the components. Heat is applied to the joining surfaces and to the soldering or brazing material until the soldering or brazing material flows. The molten material fills the area to be joined and bonds with the joining surfaces of the components. After the heat is removed, the soldering or brazing material solidifies. The result is a strong mechanical joint between the components—a joint that may also exhibit desirable electrical or thermal conduction characteristics.
One difference between soldering and brazing is the temperatures at which the two techniques are performed. Soldering typically is performed at temperatures at or below about 450° C., while brazing typically is performed at temperatures at or above 450° C. Another difference between soldering and brazing relates to the joining materials used in the two processes. Various types of materials are available for use in each process, each of the materials exhibiting different melting points. Materials having lower melting points are used in soldering, while materials with higher melting points are used in brazing. In some assembly processes, multiple components are joined in a series of separate manufacturing steps during which different bonds are formed at different temperatures. In the latter types of processes, the highest temperature joining steps are typically performed first, followed by joining steps performed at successively lower temperatures so as not to re-flow the joints created during earlier steps.
In any high temperature manufacturing process including those just described, several problems can arise in relation to holding the components together with suitable reliability and precision while the high temperature joining steps are being performed.
Such problems can be addressed beneficially with techniques that will be described below in relation to the following drawings.
This disclosure describes multiple embodiments by way of example and illustration. It is intended that characteristics and features of all described embodiments may be combined in any manner consistent with the teachings, suggestions and objectives contained herein. Thus, phrases such as “in an embodiment,” “in one embodiment,” and the like, when used to describe embodiments in a particular context, are not intended to limit the described characteristics or features only to the embodiments appearing in that context.
The phrases “based on” or “based at least in part on” refer to one or more inputs that can be used directly or indirectly in making some determination or in performing some computation. Use of those phrases herein is not intended to foreclose using additional or other inputs in making the described determination or in performing the described computation. Rather, determinations or computations so described may be based either solely on the referenced inputs or on those inputs as well as others. The phrase “configured to” as used herein means that the referenced item, when operated, can perform the described function. In this sense an item can be “configured to” perform a function even when the item is not operating and is therefore not currently performing the function. Use of the phrase “configured to” herein does not necessarily mean that the described item has been modified in some way relative to a previous state. “Coupled” as used herein refers to a connection between items. Such a connection can be direct or can be indirect through connections with other intermediate items. Terms used herein such as “including,” “comprising,” and their variants, mean “including but not limited to.” Articles of speech such as “a,” “an,” and “the” as used herein are intended to serve as singular as well as plural references except where the context clearly indicates otherwise.
Prior art techniques for holding components together during high temperature joining processes, such as soldering or brazing processes, include conventional clamps and weights.
Conventional clamps are problematic because the space between components to be joined often decreases when the brazing or soldering material disposed between them flows. Conventional clamps do not adjust to the resulting decrease in distance between the components. Consequently, they fail to maintain the force necessary to hold the components in place during the joining process. While springs have been used in attempts to cause conventional clamps to adjust to the decrease in distance between the components, springs quickly lose temper after they have been exposed to the high temperatures at which brazing and soldering are performed. (It is not uncommon, for example, to perform brazing at temperatures around 1400 degrees Fahrenheit.) Springs are therefore unsuitable for repeated use because they become permanently soft after exposure to such temperatures.
For assemblies that can be clamped vertically during the joining process, heavy weights have been placed on top of the assembly so that the force of gravity helps to keep a force applied to the components as the distance between them decreases during joining. Heavy weights, however, by definition have significant mass, and the mass of the weights must be heated to the same temperature as the workpieces in order to achieve a proper joint between the workpieces. The mass of the weights wastes energy during brazing or soldering because it absorbs heat that is generated by the oven or furnace, to no benefit. In addition, some assemblies do not lend themselves easily to vertical clamping during the joining process.
Improved techniques are therefore needed to hold components together with suitable reliability and precision while high temperature joining steps are being performed.
In embodiment 100, each of the components to be joined defines a respective joining surface 118, 120. A joining material 122 may be placed between the joining surfaces as shown. The joining material may comprise a brazing material or a soldering material, for example, suitable for the application. The clamping structure may be configured to receive the components with the joining material disposed between them such that the joining material—or, equivalently, the joining surfaces of the components—defines a joining plane 124. In such embodiments, the force may be applied in a direction substantially normal to the joining plane.
The clamping structure may be further configured to permit movement of the components 104, 106 toward one another in response to expansion of the expandable enclosure in direction 200. Such movement may enhance bonding between certain types of components as the joining material between them begins to flow when heated. In such embodiments, the expansion of expandable enclosure 108 ensures that a force is continuously applied to the components being joined—despite the reduction in distance between the components that may result when the joining material between them flows, as illustrated in
In some embodiments, the joining surfaces of the components may be allowed to move toward one another during steps 306-310, and the expandable enclosure may be allowed to expand responsive to the movement of the joining surfaces. In this manner, the force that is derived from the gas pressure within the enclosure may remain non-zero despite a reduction in distance between the components after the joining material flows and the joining surfaces of the components have moved toward one another.
In further embodiments, such as those exemplified by embodiment 100, both the clamping structure and the expandable enclosure may be configured to fit within a chamber that can be heated—such as, for example, a heating oven or furnace. For example, as illustrated in
Expandable enclosures for use in embodiments may be constructed in various ways as appropriate to a given application. In many applications, even a few thousandths of an inch of expansion may be sufficient to keep adequate force applied to a workpiece as the soldering or brazing material begins to flow and later solidifies after flowing. The amount of force generated by the expandable enclosure as it is heated may be controlled by regulating the amount of gas contained within the enclosure. Lighter weight expandable enclosures may be used for applications in which it is desirable to conserve energy during the heating process associated with flowing the joining material.
In one example class of embodiments, a suitable expandable enclosure may be fabricated from two sheets of high temperature stainless steel, such as INCONEL, which is a commercially available material manufactured by the Special Metals Corporation. The edges of the two sheets of steel may be welded around their peripheries to form a substantially airtight enclosure while the sheets themselves remain sufficiently pliable to accommodate expansion and contraction of the gas volume contained between them. For example, each sheet may have a thickness on the order of 30 thousands of an inch to achieve sufficient strength while retaining sufficient pliability. Other thicknesses may also be used. The gas volume may be inserted into the enclosure using a fill tube, which may be sealed after insertion of the gas volume. In other embodiments, the welds may be performed in an environment that is already flooded with the gas that is to be sealed within the enclosure. In the latter embodiments, no fill tube may be necessary. Instead, the ambient gas may be allowed to fill a pocket formed between the two sheets before they are welded together. In still further embodiments, the gas volume may be contained in an insertable enclosure such as a plastic bag or pillow, which may itself be sealed between the metal sheets to form the expandable enclosure.
In most applications, an inert gas would be an appropriate choice for inclusion in the expandable enclosure so as to avoid corrosion of the enclosure. For example, the gas volume may be Argon gas, Helium gas, or Neon gas. Other materials may also be used. In some applications, for example, the type of gas may be chosen according to its expansion properties.
In further embodiments, a suitable expandable enclosure may be constructed using a block of soft metal, such as Copper. In such embodiments, a void may be formed inside the block such that the void is large enough to contain the volume of gas. The walls of the block may be made thin enough to allow them to flex outwardly in response to gas pressure inside the void, but strong enough to contain the pressure inside the block at the temperatures at which the joining material flows.
In still further embodiments, a suitable expandable enclosure may be constructed by boring a hole or pocket within a block of metal, adding a rigid piston to fit within the hole or pocket, and using a sealed expandable volume or pillow of gas to drive the piston as the gas expands.
Other types of expandable enclosures may also be employed as appropriate to the application.
As persons having skill in the art will appreciate, clamping structures suitable for use in embodiments may vary depending on the application. The clamping structure, for example, may form part of a jig that is specifically adapted to the shapes and sizes of the components of the workpiece to be jointed.
By way of example, a clamping structure such as structure 102 shown in
Suitable clamp structures will be sufficiently right to enable the force derived from the gas pressure within the expandable enclosure to be applied to the workpiece as the gas volume is heated. In most applications, the clamping structure need only be snug to the workpiece before the gas volume is heated.
Depending on the construction of the expandable enclosure, it may be desirable in some embodiments to design the clamping structure such that it prevents extrusion of the expandable enclosure outside of the area under which its force is to be applied. In such embodiments, the clamping structure may be constructed as shown in
In the example embodiments shown in
In various embodiments, the force of the expandable enclosure may also be coupled to the workpiece in a direction other than the direction in which the enclosure expands.
In embodiment 800, shown in
In embodiment 900, shown in
In embodiment 1000, shown in
In any of embodiments 800, 900, 1000, the pulley, lever, or wedge arrangement may be configured to apply the force with mechanical advantage, if desired.
To accomplish joining components in more complex workpieces, it may be advantageous to apply forces in more than one direction during a joining step.
Various such clamping arrangements may be devised to apply multiple forces to a workpiece at other angles, as appropriate to a given application. The clamping elements may be held in place in any suitable manner, such as with bolts 1124 and nuts 1126 as generally described above.
In embodiments such as embodiment 1100 in which more than one expandable enclosure is employed, it is possible to apply the forces derived from the expandable enclosures in a stepped manner, if desired. That is, a force from a first expandable enclosure may be applied to the workpiece, as the assembly is heated, before a force from a second expandable enclosure is applied to the workpiece.
A variety of mechanisms may be employed to accomplish such a stepped application of forces. One such mechanism is to vary the quantity of gas in each of the enclosures. For example, the quantity of gas contained within enclosure 1116 may less than the quantity of gas contained in enclosure 1110. Either in addition to, or instead of, varying the quantity of gas in each enclosure, the two enclosures may be fitted into the clamping structure with different initial tightness. For example, clamping elements 1102/1104 may be bolted tightly against enclosure 1110 before heat is applied to the assembly, while clamping elements 1106/1108 may be bolted more loosely, so that force 1114 is applied earlier during the heating process than is force 1120. If desired, an air gap may be included between an expandable enclosure and either the adjacent clamping element or the adjacent workpiece component, or both, so that the force from the expandable enclosure is not applied to the workpiece until the enclosure has expanded to fill the air gap. Other such mechanisms may also be devised.
Any or all of the above-described apparatus elements and method steps may be combined to arrive at additional embodiments, which additional embodiments may be applied to workpieces different than those illustrated, or may be adapted to different manufacturing process than those given in the above examples.
Multiple specific embodiments have been described above and in the appended claims. Such embodiments have been provided by way of example and illustration. Persons having skill in the art and having reference to this disclosure will perceive various utilitarian combinations, modifications and generalizations of the features and characteristics of the embodiments so described. For example, steps in methods described herein may generally be performed in any order, and some steps may be omitted, while other steps may be added, except where the context clearly indicates otherwise. Similarly, components in structures described herein may be arranged in different positions or locations, and some components may be omitted, while other components may be added, except where the context clearly indicates otherwise. The scope of the disclosure is intended to include all such combinations, modifications, and generalizations as well as their equivalents.
