Patent Description:
While traditional materials suffice for typical flow containment applications involving non-corrosive materials, specialized materials are required to contain and process corrosive materials. Tantalum, titanium, and zirconium are materials that effectively handle corrosive materials. In flow sensors, for instance, Coriolis flow sensors, if an application involving corrosive flow materials is contemplated, it is often beneficial to use tantalum, titanium, and/or zirconium in order to prevent corrosion that may be experienced by more traditional materials, such as stainless steel. Incorporating tantalum, zirconium, titanium and stainless steel into a single device can be difficult. The primary methods for coupling the four materials are explosion bonding and brazing. The four materials have vastly different coefficients of thermal expansion (hereinafter, "CTEs") making traditional methods of joining the metals problematic in some contexts. For instance, when forming a flow sensor, a number of different couplings have to be formed at differing temperatures and using different materials. Because the coefficients of thermal expansion differ, the extent to which metals expand and contract in response to temperature changes varies between each material. When forming the flow sensor, if heat is used to couple elements, for instance, using one or more of brazes, welds, and solders, the expansion and contraction of different materials can cause stress in the flow sensor. The flow sensor may have existing welds and brazes that can be affected if elements coupled by those existing welds and brazes are composed of different materials and exposed to higher temperatures resulting from further brazes or welds. In particular, a high weld temperature of a material can cause a hermetically sealed braze joint within the flow sensor to reflow and fail, for instance, at temperatures above <NUM>,<NUM>°F.

Tantalum, in particular, has a high melting temperature on the order of <NUM>,<NUM>°F. Tantalum is a highly desirable material to use in Coriolis flow sensors for corrosive material applications. Typically, in order to use tantalum in a weld, the weld must be conducted at a minimum of <NUM> inches from the braze so that the heating of materials can be controlled through use of water-cooled heat sinks. With many flow sensor designs, there is insufficient space to allow intermediate heat sinks to be applied without the heat sinks melting. Without applying heat sinks, these flow sensor designs cannot incorporate tantalum or other high melting point materials without compromising the hermetic seal and potentially allowing moisture to enter the case of the flow sensor, potentially causing the flow sensor to fail.

While <CIT> describes welding a titanium insert to a flow tube to apply pressure between a process connection and a flow meter, this reference has the same limitations described above because it requires a high temperature brazing or weld procedure to couple it to the flow tube.

Accordingly, there is a need for a method of coupling and hermetically sealing elements composed of materials with different melting points and coefficients of thermal expansion.

A method for forming a pressure fit hermetic seal between a second component and an interior member is disclosed. The method comprises steps of coupling the second component to a first component by applying heat to one or more of the first component and the second component and allowing the first component and the second component to cool, wherein the applying heat step and allowing to cool step form the hermetic seal by causing compression of a hermetic element against the second component and by causing compression of the hermetic element against the interior member; and wherein the applying heat step comprises heating sufficiently such that a fusion bond is formed between the hermetic element and two or more of the first component, the second component, and the interior member.

An assembly is disclosed. The assembly comprises a first component, a second component, a hermetic element, and an interior member. The assembly has a hermetic seal formed by a method comprising steps of coupling the second component to the first component by applying heat to one or more of the first component and the second component, wherein the applying heat step comprises heating sufficiently such that a fusion bond is formed between the hermetic element and two or more of the first component, the second component, and the interior member and allowing the first component and the second component to cool. The applying heat step and allowing to cool step form the hermetic seal by causing compression of the hermetic element against the second component and by causing compression of the hermetic element against the interior member.

According to an aspect, a method for forming a pressure fit hermetic seal between a second component and an interior member is disclosed. The method comprises steps of coupling the second component to a first component by applying heat to one or more of the first component and the second component and allowing the first component and the second component to cool, wherein the applying heat step and allowing to cool step form the hermetic seal by causing compression of a hermetic element against the second component and by causing compression of the hermetic element against the interior member; and wherein the applying heat step comprises heating sufficiently such that a fusion bond is formed between the hermetic element and two or more of the first component, the second component, and the interior member.

Preferably, the hermetic element has a first end and a second end, the hermetic seal formed between the interior member and the second component having a conformal interior periphery, the hermetic seal incorporating the hermetic element. The applying heat further comprises applying heat to a heating site, the heating site on one or more of an exterior of the second component and an exterior of the first component, the heat applied when the first component is engaged with all of the second component, the hermetic element, and the interior member. The compressions are caused by expansion resulting from the applying heat step and contraction resulting from the allowing to cool step, the expansion and contraction being of portions of the first component and the second component that are heated in the applying heat step.

Preferably, the method further comprises engaging, before the coupling step, a conformal exterior of the hermetic element to a conformal interior periphery of the second component while engaging a conformal interior of the hermetic element to a portion of an exterior periphery of the interior member and engaging, before the coupling step, an abutting end of a first component with the second end of the hermetic element while engaging an interior of the first component with another portion of the exterior periphery of the interior member and while engaging a first coupling portion of the first component with a second coupling portion of the second component. The applying heat step comprises heating, at the heating site, such that at least part of the second coupling portion and the first coupling portion melt and form a weld.

Preferably, after the engaging steps but before the coupling step, the second coupling portion and the first coupling portion are engaged to at least partially overlap, the second coupling portion at least partially radially external of at least part of a cross sectional peripheral exterior of the first coupling portion.

Preferably, the hollow conformal interior at least partially conforms to the exterior of the interior member and the conformal exterior at least partially conforms to the conformal interior periphery of the second component.

Preferably, the hermetic element is composed of a material that is more malleable than the material of which one or more of the first component, the second component, and the interior member is composed.

Preferably, the compressions are compressed in compression directions, the compression directions comprising a longitudinal compression direction and a radial inward compression direction, wherein the applying heat step and the allowing to cool step are sufficient to cause a longitudinal pressure and a radial inward pressure, such that the longitudinal pressure causes a compression of at least part of the hermetic element in the longitudinal compression direction to be at least fifty thousandths of an inch and the radial inward pressure causes a compression of at least part of the hermetic element in the radial inward compression direction to be at least twenty thousandths of an inch.

According to an aspect, an assembly is disclosed. The assembly comprises a first component, a second component, a hermetic element, and an interior member. The assembly has a hermetic seal formed by a method comprising steps of coupling the second component to the first component by applying heat to one or more of the first component and the second component, wherein the applying heat step comprises heating sufficiently such that a fusion bond is formed between the hermetic element and two or more of the first component, the second component, and the interior member and allowing the first component and the second component to cool. The applying heat step and allowing to cool step form the hermetic seal by causing compression of the hermetic element against the second component and by causing compression of the hermetic element against the interior member.

Preferably, the abutting end of the first component is a first flat end and the second end of the hermetic element has a flat hermetic end.

Preferably, the conformal interior is cylindrical and the conformal exterior is in the shape of a peripheral exterior of a frustrum.

Preferably, the interior member is at least partially composed of one or more of tantalum, zirconium, and titanium and wherein one or more of the first component and the second component is at least partially composed of one or more of stainless steel and C22.

<FIG> and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of embodiments of methods for forming a hermetic seal between components of different materials. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations of these examples that fall within the scope of the present description. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of methods for forming a hermetic seal between components of different materials. As a result, the embodiments described below are not limited to the specific examples described below, but only by the claims and their equivalents.

Coupling and/or creating hermetic seals between components of vastly different thermal properties is impractical using traditional methods. For these applications, it may be best to use a pressure fit or fusion bond to create the hermetic seal between the components of materials with different properties. One way to accomplish this is to couple two components of similar materials in such a way that it causes compression of an intermediate, hermetic element between a component and another component composed of a material with vastly different properties than those of the other components. For instance, in a flow sensor that is to be used for corrosive materials, a flow tube made of tantalum may be required. Tantalum is expensive, so it does not make sense to compose an entire sensor of tantalum. It may be best to make the entire flow path that is to interact with the corrosive substance of tantalum. Welding other components to a tantalum component is problematic as tantalum melts at a significantly higher temperature than conventional, less expensive materials used in flow sensors. Also, the coefficients of expansion are vastly different, causing issues. In an embodiment, the flow tube could be composed of tantalum. It may be preferable to couple a case to a flange, the case and flange each made of conventional materials, in order to cause a weld shrink about a hermetic element (perhaps made of a more malleable material). This will cause the hermetic element to be compressed against the exterior of the flow tube and the interior of one or more of the case and the flange, creating a hermetic seal between the interior of the one or more of the case and the flange and the exterior of the hermetic element, as well as a hermetic seal between the interior of the hermetic element and the exterior of the flow tube. In so doing, a pressure fit hermetic seal between the one or more of the case and the flange made of conventional materials and the flow tube made of tantalum is possible without attempting to weld the conventional materials with the tantalum. If sufficient heat and pressure are applied, and if the components are arranged sufficiently conformally, it may be possible to further form fusion bonds between elements in addition to or instead of the pressure fit coupling, perhaps making a more robust coupling and/or hermetic seal. It should be appreciated that, while the embodiments presented are disclosed with respect to a flow sensor, embodiments are contemplated for forming hermetic seals in other devices or arrangements.

<FIG> shows a bisected side view of an embodiment of a collection <NUM> of uncoupled components. In an embodiment, the collection <NUM> of uncoupled components may be a collection of uncoupled flow sensor components. The collection <NUM> may include a first component <NUM>, a second component <NUM>, a hermetic element <NUM>, and an interior member <NUM>.

The first component <NUM> is an assembly, for instance, a component of a flow sensor. The first component may have a first coupling portion <NUM>. The first coupling portion <NUM> is a portion of the first component <NUM> that is coupled to a portion of the second component <NUM>. In an embodiment, the first coupling portion <NUM> is an external circumferential portion of the first component. The first component <NUM> may also have an abutting end <NUM>. The abutting end <NUM> abuts the hermetic element <NUM>, perhaps at a second side <NUM> of the hermetic element. In an embodiment, the abutting end <NUM> may be an optional first flat end to engage a flat hermetic end <NUM> of the hermetic element <NUM>.

The second component <NUM> is a component, perhaps of the flow sensor. In an embodiment, the second component <NUM> is different from the first component <NUM>. The second component <NUM> may have a second coupling portion <NUM>. In an embodiment, the second coupling portion <NUM> is an internal peripheral portion of the second component <NUM>. It should be appreciated that the first coupling portion <NUM> and the second coupling portion <NUM> may be external and internal peripheral (perhaps, circumferential) portions of the first component <NUM> and the second component <NUM>, respectively. The second component <NUM> may also have an interior circumference that largely conforms to the exterior of the hermetic element <NUM>. The second component <NUM> may also have a heating site <NUM> where heat is applied to the exterior of the second component <NUM>, perhaps to form a weld that facilitates the couplings herein described. Although depicted as being above and below the second component <NUM> in the limited side view, it should be understood that the heating is conducted about the periphery of the second component <NUM>, perhaps at external peripheral portions of the second component <NUM> at longitudinal portions at which the second coupling portion <NUM> overlaps the first coupling portion <NUM> when the first component <NUM> and the second component <NUM> are engaged. For the purposes of this specification, longitudinal means along the length of the interior member <NUM>. For instance, in an embodiment in which the common assembly is interior componentry of a flow sensor, the longitudinal direction will be along the flow tube <NUM>. Also, a longitudinal axis may be described as a central axis that extends along the longitudinal length of the interior member <NUM> and is centrally located in each cross section of the longitudinal length of the interior member <NUM>. For instance, in a straight tube flow sensor, the flow tube <NUM> will have a straight longitudinal axis. In a curved tube flow sensor, the longitudinal axis will conform to the center of the flow tube <NUM> at each cross section at each position of the flow tube <NUM> along the longitudinal length of the flow tube <NUM>, such that the longitudinal axis is correspondingly curved.

In another embodiment, the heating site may be alternatively or additionally on an exterior portion of the first component <NUM>. When the heating/welding is conducted, it should be appreciated that parts of one or more of the first coupling portion <NUM> and second coupling portion <NUM> may be sacrificial to the weld, forming a coupling and/or weld between the first coupling portion <NUM> and the second coupling portion <NUM>. The second component <NUM> may have an interior cavity, the interior cavity having a conformal interior periphery <NUM>. It should be appreciated that the conformal interior periphery <NUM> may be the element that is hermetically sealed with the exterior of the interior member <NUM> using the hermetic element <NUM>.

The interior member <NUM> is an interior member around which a hermetic seal is formed. Flow tube <NUM> may be an embodiment of the interior member <NUM>. The interior member <NUM> may be partially circumferentially surrounded by one or more of the first component <NUM> and the second component <NUM>. When a weld is formed between the first component <NUM> and second component <NUM> on a side of a common assembly, it can be appreciated that the interior member <NUM> may circumferentially surrounded on that side by the resulting assembly. In an embodiment, the interior member <NUM> may be an integral component of a common assembly, the common assembly perhaps being one of the first component <NUM> and the second component <NUM>.

It should be appreciated that the coupling between the first coupling portion <NUM> and the second coupling portion <NUM> may be accomplished by a weld at a site proximal to both the first and second coupling portions <NUM> and <NUM>. The heating site <NUM> is a site at which the first component <NUM> is welded to the second component <NUM>. The heating site <NUM> may be located such that the first and second coupling portions <NUM> and <NUM> are coupled by a weld at the heating site <NUM>. The heating site <NUM> may have different arrangements relative to other components in the system <NUM> when engaged and/or after coupling is finished. For instance, the heating site <NUM> may be one or more of on the exterior of a portion of the second component <NUM> at which there is some overlap between the first and second coupling portions <NUM> and <NUM> in a radial axis with respect to an interior member <NUM> (e.g. interior of flow tube <NUM>), at a position closer to a second end <NUM> of a hermetic element <NUM> than a first end <NUM> of a hermetic element, at a position "behind" <NUM> the second end <NUM> of the hermetic element (as discussed in <FIG>), at a position of overlap between a flange and a case, at a position where during a weld shrink the weld shrink will apply pressure to force a hermetic element <NUM> to create a hermetic seal between the second component <NUM> and the interior member <NUM>, and/or the like. Welding substantially cylindrical elements with circumferential welds typically requires that welds be applied at a spot with the substantially cylindrical elements rotated as the weld is being applied. In an embodiment, the heating site <NUM> will change as the components are rotated, but the heating site <NUM> may be at substantially the same longitudinal location as the elements are rotated. The heating may be quick, with the ensuing cooling beginning almost immediately.

The hermetic element <NUM> is an element that is used to form a hermetic seal between a conformal interior periphery <NUM> of the second component <NUM> and one or more of the first component <NUM> and at least part of the interior member <NUM>. In an embodiment in which the conformal interior periphery <NUM> of second component <NUM> is hermetically sealed with at least one element of the second component <NUM>, the hermetic element <NUM> may be used to form a hermetic seal as between a case <NUM> of a common assembly <NUM> and one or more of the flange <NUM> and a flow tube <NUM> of the common assembly <NUM>. An embodiment of a common assembly <NUM> with an embodiment of a case <NUM> and a flow tube <NUM> is shown and described with respect to <FIG>. An embodiment of the flange <NUM> may be shown and described with respect to <FIG>. For purposes of this specification, the terms flow tube <NUM> and interior member <NUM> may be used interchangeably, although embodiments ae contemplated in which the interior member is not a flow tube or even an element of a flow sensor. In an embodiment the hermetic element <NUM> may have a shape that conforms the hermetic element's <NUM> exterior to a conformal interior periphery <NUM> and conforms the hermetic element's <NUM> interior to another element of one of the first component <NUM> and the second component <NUM>. For instance, in an embodiment in which the first component <NUM> is a flange <NUM> and the second component <NUM> is a common assembly <NUM>, the hermetic element <NUM> may have a shape such that the exterior of the hermetic element <NUM> conforms to the interior of a case <NUM> of the common assembly <NUM> and conforms to the exterior circumference of a flow tube <NUM> of the common assembly <NUM>, such that the shape of the hermetic element <NUM> can be considered complementary to those elements to which the hermetic element <NUM> is largely conformal. Alternatively, in an embodiment in which the first component <NUM> is a common assembly <NUM> and the second component <NUM> is a flange <NUM>, the hermetic element <NUM> may have a shape such that the exterior of the hermetic element <NUM> largely conforms to the interior of the flange <NUM> and the exterior of the hermetic element <NUM> largely conforms to the external circumference of the flow tube <NUM> of a common assembly <NUM>, such that the shape of the hermetic element <NUM> can be considered complementary to those elements to which the hermetic element <NUM> is largely conformal.

In an embodiment, the hermetic element <NUM> has a hollow interior, perhaps for receiving a flow tube <NUM> of a common assembly <NUM>. The hermetic element <NUM> may have an exterior shape that is conical or substantially conical. For instance, when referring to conical shapes, the exterior conical shape is like a frustrum (e.g. a cone with its tip cut off). This would not be a complete cone or frustrum, as the center of the hermetic element <NUM> would conform to the exterior of an interior member <NUM> (necessitating the removal of the cap portion of the cone as well as the center (perhaps cylindrical) volume of the frustum) to make the "conical" or "frustum" exterior. For the purposes of this specification, the terms "conical exterior" and "frustum exterior" are meant to refer to the exterior of a frustrum or cone without the tip. The hermetic element <NUM> may have a hollow interior, the interior perhaps being cylindrical or substantially cylindrical, perhaps to receive the flow tube <NUM> of a common assembly <NUM>. The hermetic element <NUM> may also have a substantially flat hermetic end <NUM> on a second end <NUM> of the hermetic element <NUM>. The second end <NUM>, perhaps at a flat hermetic end <NUM>, may abut an abutting end <NUM> of the first component <NUM>, for instance an optional first flat end of the first component <NUM>. This combination of shapes may facilitate a wedge action when force from the weld shrink compresses the hermetic element <NUM> against the flow tube <NUM> and the conformal interior periphery <NUM> to form the hermetic seal. In alternative embodiments, the hermetic element <NUM> may be of different shapes, for instance, a shape having a cylindrical interior cavity and a cylindrical exterior. The hermetic element <NUM> may be composed of a metal that facilitates good hermetic seals, for instance, one or more of copper and brass. The hermetic element <NUM> may be composed of a material that is more malleable than the material of which the first component <NUM> is composed. The hermetic element <NUM> may be composed of a material that is more malleable than the material of which the second component <NUM> is composed. The hermetic element <NUM> may be composed of a material that is more malleable than the material of which the interior member <NUM> is composed.

In an unassembled state, the first coupling portion <NUM> may be substantially conformal to the second coupling portion <NUM>, such that when the first coupling portion <NUM> is engaged with the second coupling portion <NUM> in an unassembled state, there is very little space between the first coupling portion <NUM> and the second coupling portion <NUM>. Consequently, in this embodiment, the second coupling portion <NUM> may be considered complementary to the first coupling portion <NUM>. The relative arrangement of the second coupling portion <NUM> and the conformal interior periphery <NUM> may be such that they are separate or overlap. With respect to the assembly, if the weld is conducted on a flow sensor, the conformal interior periphery <NUM> may be at least partially proximal (to the extent they do not overlap) to the second coupling portion <NUM> (with respect to the center of the assembly formed, for instance, a flow sensor).

In an embodiment, a coupling may be formed between the first coupling portion <NUM> and the second coupling portion <NUM>. As depicted in <FIG> and <FIG>, an embodiment in which the first component <NUM> is a flange <NUM> of a flow sensor and the second component <NUM> is a common assembly <NUM> that includes a case <NUM> and flow tube <NUM> is contemplated. Embodiments in which the first component <NUM> is the common assembly <NUM> and the second component <NUM> is the flange <NUM> are contemplated as well. That is, embodiments in which an exterior portion of a flange <NUM> is coupled to an interior portion of a case <NUM> of a common assembly <NUM> (shown) and embodiments in which an exterior portion of a case <NUM> of a common assembly <NUM> is coupled to an interior portion of a flange <NUM> (not shown) are contemplated.

In various embodiments, when components have been stated as being conformal or complementary, it should be understood that the spaces between these components in an engaged and uncoupled state may be small. The spaces between any of these conformal or complementary engagements may be on the order of thousandths of an inch, for instance <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> thousandths of an inch. An effective hermetic seal may be formed by the coupling of the first component <NUM>, the second component <NUM>, and the hermetic element <NUM>, such that the hermetic element <NUM> is longitudinally compressed by, for instance, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> thousandths of an inch, and is radially compressed about the circumference of the flow tube <NUM> by, for instance, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> thousandths of an inch. The spaces may alternatively be characterized by a percentage of the outer or inner diameter of the flow tube <NUM>, for instance, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and the like percent of the outer diameter of the flow tube <NUM>.

For purposes of this specification, the common assembly <NUM> is a partially assembled interior componentry of a flow sensor. The common assembly <NUM> may have a case <NUM> and a flow tube <NUM>. The flow tube <NUM> may be composed of a material that is different from the material of which the case <NUM> and flange <NUM> are composed. The case <NUM> and the flange <NUM> may be composed of conventional materials having low CTEs and/or low melting points relative to materials used to form the flow tube <NUM>, conventional materials perhaps including, for instance, one or more of stainless steel and C22 (C22 being an alloy of nickel, chromium, molybdenum, and tungsten). The flow tube <NUM> (or interior member) may be composed of specialized materials having high CTEs and/or high melting points, for instance, one or more of tantalum, zirconium, and titanium. As mentioned, it is difficult to couple the conventional materials to the specialized materials by traditional methods. This is especially true for tantalum which has a melting point of over <NUM>°F. Welding tantalum with <NUM> series stainless steel may be impractical, as the melting point of <NUM> series stainless steel is significantly lower. The coupling of the conventional and specialized materials may be important for specific applications, such as flow sensors to be used with corrosive materials. Flow sensors used to measure corrosive materials will have a flow path that is entirely comprised of specialized materials, such that no component of the flow sensor composed of conventional materials interacts with the corrosive flow fluid.

While the coupling of this disclosure is only shown for a flange <NUM> and a common assembly <NUM> on one side of a flow sensor, it should be appreciated that these apparatus and method features may be applied to the second side of the flow sensor. Typical flow sensors may have two flanges <NUM> on terminal ends of the flow sensor in order to couple to external fluid flow elements, so the same issues with respect to creating a corrosion resistant flow path apply to both sides of a flow sensor. This may require the methods and features within to couple to the corrosion resistant elements composed of specialized materials to other elements composed of conventional materials.

In some embodiments, the hermetic seal is only formed between the conformal interior periphery <NUM>, the hermetic element <NUM> and the flow tube <NUM>. In further embodiments, the hermetic seal is formed between all of the first component <NUM>, the conformal interior periphery <NUM>, the hermetic element <NUM>, and the flow tube <NUM>. For instance, the weld shrink may be sufficient such that fusion bonds are formed between two or more of the first component <NUM>, the conformal interior periphery <NUM>, the hermetic element <NUM>, and the flow tube <NUM>. In these embodiments, the bond formed is not a simple pressure fit. However, when, in the claims, the term "pressure fit" is used, it is contemplated that the pressure fit may include embodiments in which the pressure was sufficient to establish fusion bonds such that, even when components that were pressure fit are separated, the fusion bonds do not readily disengage.

<FIG> shows a bisected side view of an embodiment of an assembly <NUM> of coupled components from <FIG>. In an embodiment, assembly <NUM> of coupled components may be coupled flow sensor components. In order to couple uncoupled components of <FIG>, the components must be engaged, and, subsequently, a weld must be formed between certain components, as is described in the methods presented with respect to the descriptions of the flowcharts. After the weld has been conducted between the first component <NUM> and the second component <NUM>, and the weld shrink creates a hermetic seal between the second component <NUM> and the flow tube <NUM> of the common assembly <NUM>, the result may appear as in <FIG>. The elements referenced in <FIG> are embodiments of the elements with the same reference numbers in <FIG>. Again, as depicted, the flange <NUM> is the first component <NUM> and the common assembly <NUM> is the second component <NUM>, but embodiments are contemplated where the common assembly <NUM> is the first component <NUM> and the flange <NUM> is the second component <NUM>. Further, embodiments are contemplated where the assembly is not a component of a flow sensor, such that the first component <NUM> and the second component <NUM> may be other things.

<FIG> shows a bisected side view of an embodiment of a common assembly <NUM>. The common assembly <NUM> has a flow tube <NUM>, a balance bar <NUM>, flow sensors 306a and 306b, driver <NUM>, support brackets 310a and 310b, and a case <NUM>.

During flow sensor manufacture, there are a number of steps in the fabrication. Typically, an intermediate step in the process is forming a common assembly <NUM> of certain components. The common assembly <NUM> is an intermediate assembly of the interior componentry of a flow sensor. Prior art assembly methods exist to assemble the common assembly <NUM>, such that any methods in this specification may start from a step in the flow sensor manufacturing process where the common assembly <NUM> is already formed. The same applies to the flange <NUM>.

The flow tube <NUM> is a component of a flow sensor through which fluid is flowed. In various applications, it is desirable to make the entire flow path in the flow sensor composed of a corrosive or heat resistant material. In these applications, embodiments of the flow tube <NUM> may be at least partially or even entirely composed of specialized materials, for instance, one or more of tantalum, zirconium, and titanium. These materials may be used in pure form or may be introduced as alloys. The flow tube <NUM> may be coupled to the interior of the common assembly, but the flow tube <NUM> may have ends protruding from the common assembly to allow flanges <NUM> to be coupled to the terminal ends. In an embodiment, there may also be a length of the flow tube <NUM> that is exposed with respect to the interior of the common assembly <NUM> around which a hermetic element <NUM> used to form a hermetic seal around the flow tube <NUM> may be situated and later compressed.

The balance bar <NUM> is a component used to provide balance to the flow tube and allow for balanced vibration of the flow tube <NUM>. The driver <NUM> is a transducer that drives vibrations in the flow tube <NUM>. Flow sensors 306a and 306b are sensors that detect vibrations of the flow tube <NUM>, perhaps detecting vibrational responses to the vibrations driven by the driver <NUM>. Coriolis flow sensors use drivers <NUM> and flow sensors 306a and 306b to determine flow fluid and/or fluid flow properties, for instance, mass flowrate, density, viscosity, and/or the like. The manners in which these measurements are conducted are well-established in the art and are omitted for brevity. The support brackets 310a and 310b are supports that fix certain elements of the flow sensor to a case <NUM>, perhaps fixing the elements via a brace bar (not shown).

The case <NUM> is a container for the flow sensor elements. The case <NUM> is typically hermetically sealed to prevent environmental fluids from entering the flow sensor. In an embodiment in which the common assembly <NUM> is the second component <NUM> (as depicted in <FIG> and <FIG>), the case <NUM> may be the element of the common assembly that has the second coupling portion <NUM>, the heating site <NUM>, and the conformal interior periphery <NUM>. In this embodiment, the hermetic seal is created between at least the conformal interior periphery <NUM> of the case <NUM> and the flow tube <NUM> using the hermetic element <NUM>. In an embodiment in which the common assembly <NUM> is the first component <NUM>, the case <NUM> may have the first coupling portion <NUM> on a part of its exterior. In this embodiment, the case <NUM> may have the abutting end <NUM> that abuts the second end <NUM> (perhaps a flat hermetic end <NUM>) of the hermetic element <NUM>, and, in this embodiment, the case <NUM> may or may not be an element of the hermetic seal.

<FIG> shows a perspective view of an embodiment of a flange <NUM>. The flange <NUM> is a terminal element in a flow sensor used to couple the flow sensor to fluid flow sources, for instance, conduits. The flange <NUM> may also participate in a hermetic seal that prevents leakage of environmental materials into places in the flow sensor not intended to receive environmental fluids. The flange <NUM> has a hollow interior <NUM> and a coupling member <NUM> having holes <NUM>. The hollow interior <NUM> is a hollow passage through which a flow tube <NUM> may be placed. The coupling member <NUM> is an element that couples the flange <NUM> and, hence, the flow sensor to external flow elements. The coupling member may have holes <NUM> to facilitate the coupling between the flange <NUM> and external flow elements.

In an embodiment in which the flange <NUM> is the second component <NUM>, the flange <NUM> may have the second coupling portion <NUM>, the heating site <NUM>, and the conformal interior periphery <NUM>. In this embodiment, the hermetic seal may be created between at least the conformal interior periphery <NUM> of the flange <NUM> and the flow tube <NUM> using the hermetic element <NUM>. In an embodiment in which the flange <NUM> is the first component <NUM> (as depicted in <FIG> and <FIG>), the flange <NUM> may have the first coupling portion <NUM> on a part of its exterior. In this embodiment, the flange <NUM> may have the abutting end <NUM> (perhaps an optional flat end <NUM> as shown) that abuts the second end <NUM> (perhaps, at a flat hermetic end <NUM>) of the hermetic element <NUM>, and in this embodiment, the flange <NUM> may or may not be an element of the hermetic seal.

<FIG> shows a perspective view of an embodiment of a hermetic element <NUM>. Hermetic element <NUM> is an embodiment of the hermetic element <NUM> described with respect to <FIG> and <FIG>. As depicted in <FIG> and <FIG>, an embodiment of the hermetic element is one having a conformal exterior <NUM> and a hollow conformal interior <NUM> that is substantially cylindrical, the hollow interior <NUM> perhaps for receiving an interior member <NUM> (e.g. flow tube <NUM>). The conformal exterior <NUM> conforms to a conformal portion of an interior of the second component. The hermetic element <NUM> may have a first end <NUM> and a second end <NUM>. In an embodiment, the second end <NUM> may be the flat hermetic end <NUM>. In an embodiment, the second end <NUM> may be wider (e.g. have a greater width or have a greater exterior diameter) than the first end <NUM>. In an embodiment, the heating site <NUM> of the invention may be "behind" <NUM> the second end <NUM>. "Behind" <NUM> may be defined by referencing a longitudinal axis that goes through the center of the hermetic element <NUM> (assuming the hermetic element <NUM> is radially symmetrical about the longitudinal axis) through a center position of the second end <NUM>, with a distal direction along this axis going from the center of the hermetic element <NUM> through the center of the second end, "behind" <NUM> being any position that is distal of the second end <NUM> in the longitudinal axis (that is with reference to the axis, not along the axis, itself). In an embodiment, a direction distally, distally measured from the center of the hermetic element <NUM> through the center of the second end <NUM>, may be considered a longitudinal axis such that any position outside of hermetic element <NUM> and distal of the second end <NUM> is "behind" <NUM> the hermetic element <NUM>. Another way to express the definition of "behind" <NUM> is to state that "behind" represents all three-dimensional space that is distal of a plane defined by the second end <NUM>. In another, potentially overlapping embodiment, the heating site <NUM> may be closer to the second end <NUM> than the first end <NUM>.

It should be appreciated that the bisected side views shown in <FIG> and later described <FIG> are merely representative of that view. Embodiments are contemplated where at least some of the elements referenced are symmetrical about the plane of bisection of the bisected view. There may be further radial symmetry about an axis along the longitudinal length of the interior member <NUM> at the center of the interior member <NUM> in vertical and transverse axes. For instance, the interior member <NUM> may be cylindrical and may have radial symmetry about a central axis, and any of the elements of <FIG> and later described <FIG> may be symmetrical about this central axis.

<FIG> show flowcharts of embodiments of methods for forming a pressure fit hermetic seal by welding. The methods disclosed in the flowcharts are non-exhaustive and merely demonstrate potential embodiments of steps and orders. The methods must be construed in the context of the entire specification, including elements disclosed in descriptions of <FIG> and <FIG>, the collection <NUM>, assembly <NUM>, common assembly <NUM>, flange <NUM>, and hermetic element <NUM> disclosed in <FIG> and <FIG>, and/or the first component <NUM>, second component <NUM>, interior member <NUM>, first coupling portion <NUM>, second coupling portion <NUM>, abutting end <NUM>, flat hermetic end <NUM>, external heating site <NUM>, conformal interior periphery <NUM>, flow tube <NUM>, balance bar <NUM>, flow sensors 306a and 306b, driver <NUM>, support brackets 310a and 310b, case <NUM>, hollow interior <NUM>, coupling member <NUM>, holes <NUM>, optional flat end <NUM>, conformal exterior <NUM>, conformal interior <NUM>, first end <NUM>, and second end <NUM>.

<FIG> shows a flowchart of an embodiment of a method <NUM> for forming a pressure fit hermetic seal by welding. In an embodiment, the method <NUM> may be an embodiment of a method for forming a hermetic seal between components of different materials. All methods, capabilities, relative arrangements, and relative couplings of all referenced elements, components and members disclosed in this specification are contemplated for accomplishing the steps of method <NUM>.

Step <NUM> is optionally, forming a first component <NUM>. The first component <NUM> may be, for instance, one of a flange <NUM> and a common assembly <NUM> (as described in the foregoing). The first component <NUM> may be formed using methods known in the art. The first component <NUM> may be formed such that it has a first coupling portion <NUM> that substantially conforms to the interior of a second component <NUM>, perhaps at a second coupling portion <NUM> of the second component <NUM>. As can be appreciated, when engaged before welding, these conforming elements may have very little space between them, perhaps on the order of thousandths of an inch or thousandths of a pipe diameter, as disclosed in this specification. In an embodiment, the first component <NUM> may be at least partially composed of one or more of stainless steel and C22.

Step <NUM> is optionally, forming a second component <NUM>. The second component <NUM> may be for instance, the other of the one of a flange <NUM> or a common assembly <NUM> (as described in the foregoing). Other embodiments are contemplated where other components are coupled to form a hermetic seal using a weld. The interior of the second component <NUM> is configured to substantially conform to the exteriors of both the hermetic element <NUM> and the first coupling portion <NUM> (as stated in step <NUM>), such that, when engaged before welding, these conforming elements may have very little space between them, perhaps on the order of thousandths of an inch or thousandths of a pipe diameter, as disclosed in this specification. In an embodiment, the second component <NUM> may be at least partially composed of one or more of stainless steel and C22.

Step <NUM> is optionally, forming a hermetic element <NUM>. The hermetic element <NUM> may be of any shape and composed of any material known in the art or as disclosed in this specification. For instance, the hermetic element <NUM> may have a conformal exterior <NUM> that conforms to the interior of the second component <NUM>, for instance, at the conformal interior periphery <NUM> of the second component <NUM>. In an embodiment, the hermetic element <NUM> may have a conical or frustrum conformal exterior <NUM> such that when pressure is applied "behind" <NUM> the hermetic element <NUM>, the conical or frustrum conformal exterior <NUM> of the hermetic element <NUM> may wedge into the conforming interior of the second component <NUM>. The hermetic element <NUM> may have a cylindrical internal cavity such that the hermetic element <NUM> may conform its interior cavity to an interior member <NUM>, for instance, a cylindrical flow tube <NUM> with a cylindrical exterior. The hermetic element <NUM> may have a first end <NUM> and a second end <NUM>. In an embodiment, the second end <NUM> may be the flat hermetic end <NUM>. In an embodiment, the second end <NUM> may be wider (e.g. have a greater width or have a greater exterior diameter) than the first end <NUM>. In an embodiment a direction distally, distally measured from the center of the hermetic element <NUM> through the second end <NUM>, may be considered a distal direction such that any area outside of and distal of the second end <NUM> is "behind" <NUM> the hermetic element <NUM>. In an embodiment, the heating site <NUM> of the invention may be "behind" <NUM> the second end <NUM>. In another, potentially overlapping embodiment, the heating site <NUM> may be closer to the second end <NUM> than the first end <NUM>. In an embodiment, the hermetic element may be formed of a material that is more malleable than the material of which one or more of the interior member <NUM>, the first component <NUM> and the second component <NUM> is formed. For instance, in an embodiment, the hermetic element <NUM> may be composed of one or more of copper or brass.

Step <NUM> is engaging the hermetic element <NUM> about the interior member <NUM>. When engaged before welding, there should be little space between the interior cavity of the hermetic element <NUM> and the exterior circumference of the interior member <NUM> (e.g. flow tube <NUM>). In an embodiment in which the first component <NUM> is a flange, step <NUM> may further comprise engaging the conformal exterior <NUM> of the hermetic element <NUM> with the interior of the second component <NUM>, perhaps such that there is little space between the conformal exterior <NUM> of the hermetic element <NUM> and the interior of the conforming portion of the second component <NUM> that conforms to the hermetic element <NUM>.

In an embodiment in which the common assembly is the first component <NUM>, Step <NUM> may involve sliding the hermetic element <NUM> onto the exterior of the interior member <NUM>, such that the flat hermetic end <NUM> is engaged with an abutting end <NUM>, perhaps an optional first flat end of the common assembly <NUM>. The reason for the difference in this and the prior described embodiment is that, in many embodiments, the interior member <NUM> (as a flow tube <NUM>) is already coupled to the common assembly <NUM>, regardless of which of the flange <NUM> and common assembly <NUM> are the first or second component <NUM> or <NUM>. In this embodiment, the interior member <NUM> may be considered "integral" to the common assembly <NUM> before the method starts. In an embodiment, the hermetic element <NUM> may be composed of one or more of tantalum, zirconium, and titanium.

Step <NUM> is engaging the first component <NUM> with the second component <NUM> and the hermetic element <NUM>. In an embodiment in which the first component <NUM> is a flange <NUM>, the hermetic element <NUM> is already engaged with the conformal portion of the second component <NUM> (a part of the interior of the common assembly <NUM>) in step <NUM>. In this embodiment, the first component <NUM> may engage its abutting end <NUM> to the second end <NUM> (perhaps, at a flat hermetic end <NUM>) of the hermetic element <NUM>. After the engaging step <NUM>, the second coupling portion <NUM> and the first coupling portion <NUM> may be engaged to at least partially overlap, the second coupling portion <NUM> at least partially radially external of at least part of a cross sectional peripheral exterior of the first coupling portion <NUM>.

In an embodiment in which the first component <NUM> is a common assembly <NUM>, the flange <NUM> may have the conformal interior periphery <NUM> for receiving the hermetic element <NUM>, such that step <NUM> involves engaging the conformal interior periphery <NUM> of the second component <NUM> with the conforming exterior of the hermetic element <NUM>.

It should be appreciated that when steps <NUM> and <NUM> are completed, the assembly having the first component <NUM>, the second component <NUM>, the hermetic element <NUM>, and the interior member <NUM> is in place with little space between the first component <NUM>, the second component <NUM>, the hermetic element <NUM>, and the interior member <NUM>. For instance, after the engaging steps, any space in a radial direction between the hermetic element <NUM> and the interior member <NUM> may be less than <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> thousandths of an inch or of an external diameter of the interior member <NUM>. While the components are conformal to an extent that little space exists between them, they may still be free floating before a weld is applied.

Step <NUM> is applying heat, at a heating site <NUM>, to the second component <NUM> and to the first component <NUM>. The heat may be such that portions of the first component <NUM> and the second component <NUM> may be melted together at the heating site <NUM>. This may create a secure weld between the first component <NUM> and second component <NUM>. The heating may be applied at a heating site <NUM> as described in this specification. For instance, the heat may be applied to melt parts of the first coupling portion <NUM> and parts of the second coupling portion <NUM>. In this embodiment, parts of the first coupling portion <NUM> and the second coupling portion <NUM> may be sacrificial to the weld. The heating site <NUM> may be located such that the first and second coupling portions <NUM> and <NUM> are coupled by a weld at the heating site <NUM>. The heating site <NUM> may have different arrangements relative to other components in the system <NUM> when assembled. For instance, the heating site <NUM> may be one or more of on the exterior of a portion of the second component <NUM> at which there is some overlap between the first and second coupling portions <NUM> and <NUM> in a radial axis with respect to an interior member <NUM> (e.g. interior of flow tube <NUM>), at a position closer to a second end <NUM> of a hermetic element <NUM> than a first end <NUM> of a hermetic element, at a position "behind" <NUM> the second end <NUM> of the hermetic element (as discussed in <FIG>), at a position of overlap between a flange and a case, at a position where, during a weld shrink, the weld shrink will apply pressure to force a hermetic element <NUM> to create a hermetic seal between the second component <NUM> and the interior member <NUM>, and/or the like.

The heating that forms the weld may also cause the materials at the side at which heat is applied to expand. This expansion may cause the abutting end <NUM> of the first component <NUM> to apply pressure longitudinally against the second end <NUM> (perhaps, at the flat hermetic end <NUM>), perhaps causing a longitudinal force applied "behind" <NUM> the hermetic element <NUM>. This may cause the conformal exterior <NUM> of the hermetic element <NUM> to be compressed against the conformal interior periphery <NUM> of the second component <NUM>. In embodiments in which the hermetic element <NUM> acts like a wedge, for instance, in embodiments where the hermetic element <NUM> has a frustum like conformal exterior <NUM>, the longitudinal pressure will translate to radial inward pressure. The expansion of the second component <NUM> may also cause a radial inward pressure. The radial inward pressure may compress the conformal interior periphery <NUM> against the conformal exterior <NUM> of the hermetic element <NUM> and may compress the hermetic element <NUM> such that the conformal interior <NUM> of the hermetic element <NUM> is compressed against the exterior of the interior member <NUM>. This may represent a start of forming a pressure fit between the hermetic element <NUM>, the second component <NUM>, and the interior member <NUM> to begin forming the hermetic seal that at least hermetically seals the conformal interior periphery <NUM> of the second component <NUM> with the exterior of the interior member <NUM> via pressure fit of the hermetic element <NUM>. It should be appreciated that, once this pressure is applied, one or more of the conformal interior periphery <NUM> and the hermetic element <NUM> may partially deform to form the pressure fit that leads to the hermetic seal. In embodiments in which the hermetic element <NUM> is more malleable than other components, the hermetic element <NUM> may be the element that is compressed. In an embodiment, sufficient heat is provided such that, after the heating step <NUM> and cooling step <NUM> are finished, a fusion bond forms between two or more of the first component <NUM>, the second component <NUM>, the hermetic element <NUM>, and the interior member <NUM>. In an embodiment, the heating applied in step <NUM> may not be sufficient and/or the heating site <NUM> may be too distant from the hermetic element <NUM> to melt the hermetic element <NUM>.

Step <NUM> is allowing the assembled components to cool. This step involves letting all components cool, for instance, letting one or more of the first component <NUM>, second component <NUM>, hermetic element <NUM>, and the interior member <NUM> cool. While the heating may cause longitudinal pressure to force the hermetic element <NUM> against the conformal interior periphery <NUM>, it may not be sufficient to create a hermetic seal between the hermetic element <NUM> and the interior member <NUM>. Cooling causes contraction in the entire system. This means that conformal interior periphery <NUM> will compress in both radial and longitudinal directions, causing direct radial inward compression that is reinforced by translated longitudinal compression to radially inwardly conform the conformal interior periphery <NUM> to the conformal exterior <NUM> of the hermetic element <NUM> and the conformal interior <NUM> of the hermetic element <NUM> to the exterior of the interior member <NUM>, causing a hermetic seal between the conformal interior periphery <NUM> and the interior member <NUM> via the hermetic element <NUM>. This may be further reinforced by longitudinal forces generated by the longitudinal contraction of one or more of the first component <NUM> and the second component <NUM> during cooling. The contraction of the first component <NUM>, which may abut the hermetic element <NUM>, may cause longitudinal compression against the hermetic element <NUM> that may further compress the hermetic element's <NUM> conformal exterior <NUM> to the conformal interior periphery <NUM> of the second component <NUM>. Also, in embodiments where the conformal exterior <NUM> of the hermetic element <NUM> acts as a wedge (e.g. if the conformal exterior <NUM> is shaped like a frustum) some of the longitudinal compression caused by contraction of the first component <NUM> is again translated, via the shape of the conformal exterior <NUM> of the hermetic element <NUM> and the shape of the conformal interior periphery <NUM> of the second component <NUM>, such that further compression is generated radially inwardly and internally to cause the hermetic element <NUM> to compress and make a hermetic seal. Again, the further inward radial compression of the conformal exterior <NUM> of the hermetic element against conformal interior periphery <NUM> causes the hermetic element <NUM> to compress radially inwardly around the circumference of the interior member <NUM> to make a hermetic seal between the conformal interior <NUM> of the hermetic element <NUM> and the exterior of the interior member <NUM>.

It should be understood that a circumferential weld may require rotation of elements about an axis. In the embodiments disclosed, a heating site <NUM> would be heated while the assembly is rotated, in order to create a circumferential weld. When implementing steps <NUM> and <NUM>, it should be understood that some portions of the circumference of the assembly will be heated and cooled before others. In this embodiment, during the rotation, the heating and cooling may be conducted quickly at each position. Also, heat may or may not be applied to the entire circumference of the welding site simultaneously. Heat is typically applied at a single position, and the assembly is rotated to weld the entire periphery at substantially the same longitudinal position about the circumference of the assembly. As such, step <NUM> is conducted at one position, and step <NUM> at that position may be occurring simultaneously with step <NUM> at a new position that is approached by a heating element, such as a welder, when the assembly is rotated. This means that different portions of the assembly may be welded at different times, perhaps making steps <NUM> and <NUM> sequential only for a particular position on a circumferential weld facilitated by rotating the assembly.

In an embodiment, the applying heat step <NUM> and the allowing to cool step <NUM> are sufficient to cause a longitudinal pressure <NUM> and a radial inward pressure <NUM>, such that the longitudinal pressure <NUM> causes a compression of at least part of the hermetic element <NUM> in the longitudinal compression direction to be at least fifty thousandths of an inch and the radial inward pressure <NUM> causes a compression of at least part of the hermetic element <NUM> in the radial inward compression direction to be at least twenty thousandths of an inch.

In an embodiment, a final product of steps <NUM> to <NUM> may be an assembly <NUM>. Of course, the assembly <NUM> need not only be formed on one side of the common assembly <NUM>. It may be advantageous to generate a pressure fit hermetic seal on another side of the common assembly <NUM>. While the embodiments disclosed reflect flow sensors, it should be understood that these method steps may apply to any context in which one or more hermetic seals need to be formed.

Step <NUM> is optionally, repeating steps <NUM> to <NUM> for another side of an assembly. In an embodiment, the overall resulting apparatus may be a flow sensor. Flow sensors typically have at least two flanges <NUM> to be coupled to opposing ends of a common assembly <NUM> to form a flowmeter. Step <NUM> repeats steps <NUM> to <NUM> for another side of a flow sensor in order to complete the hermetic seal for both sides of the flow sensor. This may entail a hermetic seal at each of the flanges <NUM> or a hermetic seal at each of the common assembly <NUM> ends. Further embodiments are contemplated in which the hermetic seals are made as between all of the flange <NUM>, an end of the common assembly <NUM>, the flow tube <NUM>, and the hermetic element <NUM>.

In an embodiment, each of the steps of the method shown in <FIG> is a distinct step. In another embodiment, although depicted as distinct steps in <FIG>, steps <NUM>-<NUM> may not be distinct steps. In other embodiments, the method shown in <FIG> may not have all of the above steps and/or may have other steps in addition to or instead of those listed above. The steps of the method <NUM> shown in <FIG> may be performed in another order. Subsets of the steps listed above as part of the method <NUM> shown in <FIG> may be used to form their own method. The steps of method <NUM> may be repeated in any combination and order any number of times, for instance, continuously looping in order to form multiple hermetic seals, perhaps, for one or more flow sensors.

Step <NUM> is forming a hermetic seal between a second component <NUM> and an interior member <NUM> by coupling the second component <NUM> to the first component <NUM> by applying heat and forming the hermetic seal by compression of a hermetic element <NUM> against the second component <NUM> and by compression of the hermetic element <NUM> against the interior member <NUM>, the compression resulting from the heating. In an embodiment, step <NUM> may involve embodiments of two or more of steps <NUM>-<NUM>. In an embodiment, step <NUM> is forming a pressure fit hermetic seal between a second component <NUM> and an interior member <NUM>, comprising coupling the second component <NUM> to the first component <NUM> by applying heat to one or more of the first component <NUM> and the second component <NUM> and allowing the first component <NUM> and the second component <NUM> to cool, wherein the applying heat step and allowing to cool step form the hermetic seal by causing compression of a hermetic element <NUM> against the second component <NUM> and by causing compression of the hermetic element <NUM> against the interior member <NUM>. In an embodiment, step <NUM> may involve coupling the second component <NUM> to the first component <NUM> by applying heat to a heating site <NUM> on the exterior of the second component <NUM> when the first component <NUM> is engaged with all of the second component <NUM>, the hermetic element <NUM>, and the interior member <NUM>, allowing the first component <NUM> and the second component <NUM> to cool, wherein the applying heat and allowing to cool steps form the hermetic seal by compression of a hermetic element <NUM> against the second component <NUM> and by compression of the hermetic element <NUM> against the interior member <NUM>, the compressions resulting from expansion and contraction of heated portions of the first component <NUM> and the second component <NUM>.

It should be understood that a circumferential weld requires rotation of elements about an axis. In the embodiments disclosed, a heating site <NUM> would be heated while the assembly is rotated, in order to create a circumferential weld. When implementing heating and allowing to cool steps, it should be understood that some portions of the circumference of the assembly will be heated and allowed to cool before others. In this embodiment, during the rotation, the heating and allowing to cool are conducted quickly at each position. Also, heat may not be applied to the entire circumference of the welding site simultaneously. Heat may be applied at a single position, and the assembly is rotated to weld the entire periphery at substantially the same longitudinal position about the circumference of the assembly. As such, heating is conducted at one position, and allowing to cool at that position may be occurring simultaneously with heating at a new position that is approached by a heating element, such as a welder, when the assembly is rotated. This means that different portions of the assembly may be welded at different times, perhaps making heating and allowing to cool steps sequential only for a particular position on a circumferential weld facilitated by rotating the assembly.

In other embodiments, the method shown in <FIG> may have other steps in addition to or instead of the step listed above. Subsets of the step listed above as part of the method <NUM> shown in <FIG> may be used to form their own method. The step of method <NUM> may be repeated any number of times, for instance, continuously looping in order to form multiple hermetic seals, perhaps, for one or more flow sensors.

<FIG> show illustrations explaining an embodiment of a progression of the pressure fit hermetic seal formed by welding described in the specification. These illustrations demonstrate embodiments of the relative position of items and the directions of pressure applied. For purposes of <FIG> the "components" refer to the first component <NUM> (illustrated as a flange <NUM>), the second component (illustrated as a common assembly <NUM>), the hermetic element <NUM>, and the interior member <NUM> (illustrated as flow tube <NUM> that is already integrated into the common assembly <NUM>).

<FIG> shows an illustration of a bisected side view of an embodiment of uncoupled components 800A before engagement or welding. The components are uncoupled, as is shown in <FIG>.

<FIG> shows an illustration of a bisected side view of an embodiment of uncoupled components 800B after the components are engaged but before a weld. The components may have small spaces between them, but the components may be largely complementary and conformal, limiting those spaces. The first coupling portion <NUM> may be conformal with the second coupling portion <NUM> (reference numbers not shown but are shown in prior figures). The conformal interior periphery <NUM> of the second component <NUM> conforms to the conformal exterior <NUM> of the hermetic element <NUM>. The conformal interior <NUM> of the hermetic element <NUM> conforms to the exterior of the interior member <NUM> (e.g. flow tube <NUM>). The abutting end <NUM> may at least partially conform to the second end <NUM> (perhaps, the flat hermetic end <NUM>).

<FIG> shows an illustration of a bisected side view of an embodiment of components 800C when heat is applied to a heating site <NUM> to form a weld between the second component <NUM> and the first component <NUM>. Although not shown, parts of each of the first coupling portion <NUM> and the second coupling portion <NUM> may be sacrificial to the weld. The heating causes expansion of the components. The expansion can be described as longitudinal expansion <NUM> and radial expansion <NUM>. In the embodiment shown, the heat is applied "behind" <NUM> the second end <NUM> of the hermetic element <NUM>. The longitudinal expansion <NUM> of heated portions of the first component <NUM> and the second component <NUM> causes a longitudinal pressure <NUM> against the hermetic element <NUM>, compressing the hermetic element <NUM> against the conformal interior periphery <NUM> of the second component <NUM>. In an embodiment where the hermetic element <NUM> may act as a wedge (for instance, if the exterior shape of the hermetic element is like a frustum), some of the longitudinal pressure <NUM> may be translated in a radial inward direction to generate some radial inward pressure <NUM> which may cause some radial compression of the hermetic element <NUM> against the conformal interior periphery <NUM> and some radial compression of the hermetic element <NUM> about the interior member <NUM>.

The radial expansion <NUM> causes direct radial inward pressure <NUM>. This may cause the conformal interior periphery <NUM> of the second component <NUM> to compress the hermetic element <NUM> at the conformal exterior <NUM> and cause translated compression through the hermetic element <NUM> to compress the conformal interior <NUM> of the hermetic element <NUM> against the exterior of the interior member <NUM>. These compressions begin to form the hermetic seal by pressure fit. In an embodiment where the hermetic element <NUM> may act as a wedge (for instance, when the conformal exterior <NUM> is shaped like a frustum), some of the radial inward pressure <NUM> may be translated to longitudinal pressure <NUM>.

<FIG> shows an illustration of a bisected side view of an embodiment of components 800D when the components are allowed to cool after the weld. After heating, the site of the weld is allowed to cool (perhaps by rotating to a next heating site <NUM>). The resulting coupling formed between the first component <NUM> and the second component <NUM> fixes relative positions of the first and second components <NUM> and <NUM>. The portions of the first component <NUM> and the second component <NUM> that were heated contract when allowed to cool. The contractions can be described as longitudinal contractions <NUM> and radial contractions <NUM>. The longitudinal contractions <NUM> directly cause a longitudinal pressure <NUM>. The radial contractions <NUM> directly cause a radial inward pressure <NUM>. It should be understood that the contractions may also cause translated pressures, such that the longitudinal contractions <NUM> cause some translated radial inward pressure <NUM> and radial contractions <NUM> may cause some translated longitudinal pressure <NUM> (for instance, in embodiments where the conformal exterior <NUM> of the hermetic element <NUM> is shaped like a frustum and/or acts as a wedge). The heated portions of components <NUM> and <NUM> contract when allowed to cool such that one or more of the conformal interior periphery <NUM> compresses the hermetic element <NUM> radially at the conformal exterior <NUM> of the hermetic element <NUM>, causing further translated radial inward compression of the hermetic element <NUM> at the conformal interior <NUM> of the hermetic element <NUM> and the exterior of the interior member <NUM> (e.g. a flow tube <NUM>). The contraction further causes one or more of the first component <NUM> and the second component <NUM> to compress the hermetic element <NUM> longitudinally against the conformal interior periphery <NUM>. After heating and allowing to cool steps are completed, a hermetic seal is formed between the conformal interior periphery <NUM> of the second component <NUM>, the hermetic element <NUM>, and the interior member <NUM>.

As stated above, the circumferential heating is applied only at one position at a time, with the assembly being rotated to allow the heating element to move along a substantially circumferential path at substantially the same longitudinal position. The embodiments shown in <FIG> and <FIG> show only heating for one position. The assembly may be rotated while the heat is applied such that a circumferential or peripheral weld is formed about a circumference of the assembly at a particular longitudinal position with respect to the assembly. It can be appreciated that, as more positions along the circumference are heated and subsequently allowed to cool, the components may be coupled more closely, eliminating more space between the components and facilitating the hermetic seal. As stated, in an embodiment, the hermetic seal may be accomplished solely by a pressure fit. However, if sufficient heat is applied with correct relative conformal positions of components, a fusion bond may further be formed between two or more of the components. This fusion bond generated in those embodiments could be in addition to or instead of the pressure fit.

<FIG> shows an illustration of a bisected side view of an embodiment of an assembly 800E formed after the components are welded and allowed to cool. The assembly 800E may be an embodiment of assembly <NUM>. At least some of the small spaces that existed are absent because a hermetic seal has been formed. The hermetic seal may be as between certain specific elements (eliminating spaces that would prevent a hermetic seal), such as between the conformal interior periphery <NUM> and the interior member <NUM>, and the hermetic element <NUM>. This may represent an external hermetic seal <NUM> between at least part of the conformal interior periphery <NUM> and at least part of the conformal exterior <NUM> of the hermetic element <NUM> and an internal hermetic seal <NUM> between at least part of the conformal interior <NUM> of the hermetic element <NUM> and at least part of the interior member <NUM>. In another embodiment, the hermetic seal may be as between the conformal interior periphery <NUM>, the hermetic element <NUM>, the interior member <NUM>, and the first component <NUM>. This may represent an external hermetic seal <NUM> between the conformal interior periphery <NUM> and the conformal exterior <NUM> of the hermetic element <NUM>, an internal hermetic seal <NUM> between the conformal interior <NUM> of the hermetic element <NUM> and the interior member <NUM>, and another hermetic seal (not shown) between the abutting end <NUM> and the second end <NUM> (perhaps, at the flat hermetic end <NUM>) of the hermetic element <NUM>. It is also contemplated that the pressures applied may further cause fusion bonding between any of the components, perhaps further securing the hermetic seal. It can be seen that, after the welding is completed, a weld <NUM> composed of all of the weld beads formed around the perimeter of the assembly is formed by the heating.

The detailed descriptions of the above embodiments are not exhaustive descriptions of all embodiments contemplated by the inventors to be within the scope of the present description. Indeed, persons skilled in the art will recognize that certain elements of the above-described embodiments may variously be combined or eliminated to create further embodiments, and such further embodiments fall within the scope and teachings of the present description. It will also be apparent to those of ordinary skill in the art that the above-described embodiments may be combined in whole or in part to create additional embodiments within the scope and teachings of the present description. When specific numbers representing parameter values are specified, the ranges between all of those numbers as well as ranges above and ranges below those numbers are contemplated and disclosed.

Claim 1:
A method for forming a pressure fit hermetic seal between a second component (<NUM>) and an interior member (<NUM>), the method comprising:
coupling the second component (<NUM>) to a first component (<NUM>) by applying heat to one or more of the first component (<NUM>) and the second component (<NUM>); and
allowing the first component (<NUM>) and the second component (<NUM>) to cool,
characterized in that: the applying heat step and allowing to cool step form the hermetic seal by causing compression of a hermetic element (<NUM>) against the second component (<NUM>) and by causing compression of the hermetic element (<NUM>) against the interior member (<NUM>); and wherein the applying heat step comprises heating sufficiently such that a fusion bond is formed between the hermetic element (<NUM>) and two or more of the first component (<NUM>), the second component (<NUM>), and the interior member (<NUM>).