Patent Description:
The present invention relates generally to metal adapters, and specifically to a dual metal adapter for resistive heating applications.

Several techniques are available for joining metal parts together, including resistive brazing/soldering and spot welding. Both techniques use high current to heat parts. More specifically, brazing/soldering uses a filler metal that melts to create joints whereas spot welding melts the base materials to create a joint.

For each technique, high current flows into the top conductor of the tool, through one electrode, through the parts being joined, out the other electrode, and then out of the bottom conductor. Most of the heat is generated in the electrodes and then conducts into the parts being joined, thereby indirectly heating the parts. As a result, the electrodes get very hot and eventually wear. By definition, since most the heat is generated in the electrodes, the electrodes need to be hotter than the parts to be joined and heat must be able to flow out of the electrodes into the parts. <CIT> discloses a tubular metal nipple for joining with the end of a copper tube by solder, having an inner copper sleeve and a steel outer casing, with a layer of brazing material bonding the sleeve to the outer casing. <CIT> discloses a tubular sleeve placed between a first body and a second body to bond them together using a locking abutment. <CIT> discloses a copper and steel composite pipe, wherein copper and steel pipes are welded together.

An assembly according to the invention is defined in claim <NUM>. The assembly includes at least two members having first and second ends. A dual metal adapter, separate from the at least two members, for connecting to the at least two members includes an inner tube having an outer surface and a first inner surface, the first inner surface sized and shaped to receive and contact the first end of the at least two members and being formed from a first metal having a first resistivity. The dual metal adapter also includes an outer tube having a second inner surface, the second inner surface extending over the inner tube, wherein the outer surface of the inner tube and the second inner surface are tightly held together via friction fit. The outer tube is formed from a second metal having a second resistivity greater than the first resistivity. The first end of the at least two members is metallurgically bonded to the inner tube.

In another example, an assembly includes a first tubular member having first and second ends and a second tubular member having first and second ends. A dual metal adapter for connecting to the first ends of the first and second members includes an inner tube for receiving and contacting the first ends of the first and second members and being formed from a first metal having a first resistivity. An outer tube extends over the inner tube and is secured thereto. The outer tube is formed from a second metal having a second resistivity greater than the first resistivity. Pockets are provided between ends of the inner tube and ends of the outer tube. Filler metal is positioned within each of the pockets. The first ends of the first and second members are metallurgically bonded to the inner tube by the filler metal in response to heat applied to the assembly.

In another example, a dual metal adapter for connecting to an end of at least one member includes an inner tube for receiving and contacting the end of the at least one member and being formed from a first metal having a first resistivity. An outer tube extends over the inner tube and is secured thereto. The outer tube is formed from a second metal having a second resistivity greater than the first resistivity. The at least one member is metallurgically bonded to the inner tube in response to heat applied to the outer tube. The first and second metals have melting points greater than about <NUM>.

In another example, a method of forming an assembly includes inserting an inner tube formed from a first metal having a first resistivity into an outer tube formed from a second metal having a second resistivity greater than the first resistivity. The inner and outer tubes are secured together. At least one member having first and second ends is inserted into the inner tube. The first end of the at least one member is metallurgically bonded to the inner tube.

Other objects and advantages and a fuller understanding of the invention will be had from the following detailed description and the accompanying drawings.

The present invention relates generally to metal adapters, and specifically to a dual metal adapter for resistive heating applications. The dual metal adapter can be used in a variety of applications, including forming liquid cooling devices for rotary electric machines. In such applications, the adapter functions as a fluid coupling. Example cooling devices are shown and described in <CIT> and <CIT>, and <CIT>, the entirety of which are incorporated by reference herein.

An example dual metal adapter <NUM> and assembly <NUM> formed therefrom are shown in <FIG>. The assembly <NUM> includes at least one member metallurgically bonded to the adapter <NUM>. As shown, first and second members <NUM>, <NUM> are metallurgically bonded to the adapter <NUM> and extend in opposite directions therefrom.

The first and second members <NUM>, <NUM> can be tubular (as shown) or solid (not shown). For instance, the first member <NUM> can be a tubular member fluidly connected to a fluid manifold in a rotary electric machine and the second member <NUM> can be a tubular member fluidly connected to an in-slot cooling device in the rotary electric machine (not shown). Referring to <FIG>, the first member <NUM> is elongated and extends along a centerline <NUM> from a first end <NUM> to a second end <NUM>. A passage <NUM> extends the entire length of the first member <NUM>. The first member <NUM> includes an outer surface <NUM>.

The second member <NUM> (<FIG>) is elongated and extends along a centerline <NUM> from a first end <NUM> to a second end <NUM>. A passage <NUM> extends the entire length of the second member <NUM>. The second member <NUM> includes an outer surface <NUM>. The first and second members <NUM>, <NUM> can each be made of a metal having a relatively lower resistivity, e.g., copper or aluminum, compared to other metals. The longitudinal cross-section of the first and second members <NUM>, <NUM> can be circular (as shown), triangular or polygonal (not shown).

The adapter <NUM> includes an outer tube <NUM> and an inner tube <NUM> provided therein. The inner and outer tubes <NUM>, <NUM> can have any cross-sectional shape, e.g., circular, triangular, square, polygonal, etc. Although the inner and outer tubes are illustrated as separate, stand-alone tubes, it will be appreciated that the tubes can be defined and embodied in different manners. For example, the inner and outer tubes can be arranged in pairs each forming the leg of a T-shaped or H-shaped adapter. Alternatively, one or both of the inner and outer tubes can be formed in or defined by a block of material, e.g., an end cap or fluid manifold. For instance, the outer tube can constitute a tubular surface defining a passage extending through or into a solid block of material and the inner tube can be inserted therein.

In the example shown in <FIG>, the outer tube <NUM> extends along a centerline <NUM> from a first end <NUM> to a second end <NUM>. An inner surface <NUM> defines a passage <NUM> extending the entire length of the outer tube <NUM>. Alternatively, the passage <NUM> can terminate prior to the second end <NUM> (not shown). The outer tube <NUM> is made of a metal having a first resistivity. This can include, for example, steel, stainless steel, etc. The inner surface <NUM> of the outer tube <NUM> can also be coated, plated or otherwise provided with a layer of copper (not shown).

The inner tube <NUM> (<FIG>) extends along a centerline <NUM> from a first end <NUM> to a second end <NUM>. An inner surface <NUM> defines a passage <NUM> extending the entire length of the inner tube <NUM>. The inner surface <NUM> has the same longitudinal cross-sectional shape as the first and second member <NUM>, <NUM>. The inner tube <NUM> includes an outer surface <NUM> having the same longitudinal cross-sectional shape as the passage <NUM> of the outer tube <NUM>. The inner tube <NUM> is made of a metal having a second resistivity less than the first resistivity. This can include, for example, copper or aluminum. The inner and outer tubes <NUM>, <NUM> can be formed from one or more materials having a melting point greater than about <NUM>.

Referring to <FIG>, the inner tube <NUM> is positioned within the passage <NUM> of the outer tube <NUM>. The inner tube <NUM> is shorter than the outer tube <NUM> such that a pocket <NUM> is defined in the passage <NUM> between the first ends <NUM>, <NUM> of the tubes <NUM>, <NUM>. Another pocket <NUM> is defined in the passage <NUM> between the second ends <NUM>, <NUM> of the tubes <NUM>, <NUM>. The outer surface <NUM> of the inner tube <NUM> and the inner surface <NUM> of the outer tube <NUM> are configured such that the tubes are tightly held together via friction fit.

Once the inner tube <NUM> is positioned within the passage <NUM> of the outer tube <NUM> (see <FIG>), a filler metal <NUM> is positioned within each pocket <NUM>, <NUM>. The filler metal <NUM> can be a pre-formed brazing filler metal or a soldering filler metal. In any case, the filler metal <NUM> has a melting point lower than the melting point of both the inner tube <NUM> material and the outer tube <NUM> material. The filler metal <NUM> has a melting point lower than the melting point of both the first and second members <NUM>, <NUM>. In one instance, the filler metal <NUM> has a melting point between about <NUM> and about <NUM>.

The first end <NUM> of the first member <NUM> is inserted axially into the passage <NUM> of the inner tube <NUM> in the manner indicated at A<NUM>. The first end <NUM> of the second member <NUM> is inserted axially into the passage <NUM> of the inner tube <NUM> in the manner indicated at A<NUM>. The first ends <NUM>, <NUM> are positioned or held spaced from one another within the passage <NUM> by an axial gap <NUM>. The outer surfaces <NUM>, <NUM> of the first and second members <NUM>, <NUM> contact the inner surface <NUM> of the inner tube <NUM>.

A pair of electrodes <NUM>, <NUM> are placed in contact with the exterior of the outer tube <NUM> and electrically connected to a current source <NUM> in a closed loop. The electrodes <NUM>, <NUM> can be positioned on opposite sides, e.g., diametrically opposed, from one another (as shown) or at opposite ends <NUM>, <NUM> of the outer tube <NUM> (not shown). The outer tube <NUM> can include flat or planar tabs (not shown) extending from the outer surface to facilitate connecting the electrodes <NUM>, <NUM> thereto.

Regardless, current supplied to the electrode <NUM> and passes through the outer tube <NUM>, the inner tube <NUM>, and the electrode <NUM> in succession, then returns to the current source <NUM>. In other words, current can flow back and forth between the electrodes <NUM>, <NUM> and through the tubes <NUM>, <NUM>. Since the outer tube <NUM> is formed from a high resistivity material, heat is generated primarily in the outer tube as opposed to within the electrodes <NUM>, <NUM>. It will be appreciated that the outer tube <NUM> can alternatively be directly heated with a heat source (not shown) instead of applying current to the outer tube.

The heat conducts radially inwards from the outer tube <NUM> to the inner tube <NUM> and filler metals <NUM>. As the current is further applied, the temperature rises until the filler metal <NUM> melts and metallurgically bonds the inner tube <NUM> to the first and second members <NUM>, <NUM>. Since the inner and outer tubes <NUM>, <NUM> are mechanically connected together via friction fit, the tubes <NUM>, <NUM> and members <NUM>, <NUM> become securely fastened to one another.

The dual metal adapter shown and described herein is advantageous in that it readily allows lower resistivity components, such as copper first and second members, to be metallurgically bonded to the adapter, which is not feasible with current heating systems. More specifically, since the outer tube has a higher resistivity than the inner tube, most heat generated in the adapter resides in the outer tube and conducts radially inward to the inner tube. This enables direct heating - and ultimately melting - of the braze/solder filler metal and metallurgically bonds the inner tube to the first and second members. This direct heating of the inner tube and filler metal by the outer tube (as opposed to indirect heating by the electrodes) enables less current to be used to secure the members to the adapter than is typically required in resistive heating applications. Moreover, since less current is used the electrodes reach lower temperatures, thereby prolonging their lifespan.

Additionally, the adapter shown and described herein utilizes only a few simply constructed components and does not require any moving parts to either secure the member(s) to the adapter or enable fluid flow between first and second tubular members secured to the adapter.

Claim 1:
An assembly (<NUM>) comprising:
at least two members (<NUM>, <NUM>) including first (<NUM>, <NUM>) and second ends (<NUM>, <NUM>);
a dual metal adapter (<NUM>), separate from the at least two members, for connecting to the at least two members, comprising:
an inner tube (<NUM>) having an outer surface (<NUM>) and a first inner surface (<NUM>), the first inner surface sized and shaped to receive and contact the first ends of the at least two members, and being formed from a first metal having a first resistivity; and
an outer tube (<NUM>) having a second inner surface (<NUM>), the second inner surface extending over the inner tube, wherein the outer surface of the inner tube and the second inner surface are tightly held together via friction fit, the outer tube being formed from a second metal having a second resistivity greater than the first resistivity, each of the first ends of the at least two members being metallurgically bonded to the inner tube.