Patent Description:
Refill friction stir spot welding is a solid state joining process. It can be used to weld two or more overlapping metal workpieces. In refill friction stir spot welding, a sleeve and a pin within the sleeve are pressed against one of the workpieces and rotated to heat the workpieces. The workpiece material achieves a plastic state from heat and pressure. The sleeve is pushed into the workpiece while the pin is retracted away from the workpiece, which causes a displacement of the plastic workpiece material within the sleeve. The sleeve and pin are then returned to their initial flush condition to force the displaced material back toward the workpieces, thereby forming a generally flush spot weld. Refill friction stir spot welding devices can be mounted to robot arms (e.g., a <NUM>-axis robot arm) and gantry-style welding tables for automated spot welding, and also pedestal-style machines.

Over time, refill friction stir spot welding tools can become clogged, worn, etc. so that they require periodic replacement. Replacing refill friction stir spot welding tools is typically labor-intensive and time-consuming, and, thus, can be expensive and lead to undesirable down time. It would be desirable to minimize the time required to replace refill friction stir spot welding tools in a refill friction stir spot welding device. Document <CIT> discloses a counter-rotating spindle including a shoulder tool, a pin tool inserted in the shoulder tool, a first motor that is connected with the pin tool and rotates the pin tool, and a second motor that is connected with the shoulder tool and rotates the shoulder tool.

The following summary presents a simplified summary in order to provide a basic understanding of some aspects of the devices, systems and/or methods discussed herein. This summary is not an extensive overview of the devices, systems and/or methods discussed herein. It is not intended to identify critical elements or to delineate the scope of such devices, systems and/or methods. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

In accordance with one aspect of the present invention, provided is a quick connect refill friction stir spot welding tool according to claim <NUM>. In accordance with a preferred embodiment of the present invention, the friction pin comprises a stadium-shaped mounting head receivable by the spindle of the refill friction stir spot welding end effector. The clamp is attachable to and detachable from the refill friction stir spot welding end effector by rotations of the clamp relative to clamp receiver through less than <NUM> degrees. The friction sleeve and friction pin are attachable to and detachable from the refill friction stir spot welding end effector by rotations of the friction sleeve and friction pin relative to the spindle through less than <NUM> degrees.

In accordance with another aspect of the present invention, provided is a refill friction stir spot welding end effector for a robot arm in accordance with claim <NUM>.

The foregoing and other aspects of the invention will become apparent to those skilled in the art to which the invention relates upon reading the following description with reference to the accompanying drawings, in which:.

The present invention relates to refill friction stir spot welding devices, such as robotic refill friction stir spot welding tools and end effectors. The present invention will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. It is to be appreciated that the various drawings are not necessarily drawn to scale from one figure to another nor inside a given figure, and in particular that the size of the components are arbitrarily drawn for facilitating the understanding of the drawings. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It may be evident, however, that the present invention can be practiced without these specific details. Additionally, other embodiments of the invention are possible and the invention is capable of being practiced and carried out in ways other than as described. The terminology and phraseology used in describing the invention is employed for the purpose of promoting an understanding of the invention and should not be taken as limiting.

As used herein, "at least one", "one or more", and "and/or" are openended expressions that are both conjunctive and disjunctive in operation. Any disjunctive word or phrase presenting two or more alternative terms, whether in the description of embodiments, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" should be understood to include the possibilities of "A" or "B" or "A and B.

<FIG> schematically shows a refill friction stir spot welding process. Refill friction stir spot welding is a solid state joining process. The workpieces <NUM>, <NUM> do not melt during welding, but are heated to a plastic state. A tool <NUM> that performs the spot weld includes a non-rotating clamp <NUM>, a rotating friction sleeve <NUM>, and a rotating friction pin <NUM>. The workpieces <NUM>, <NUM> to be spot welded are clamped between the tool <NUM> and a support base or anvil <NUM>. Pressure is applied to the clamped workpieces <NUM>, <NUM> and the workpieces are locally heated by the friction sleeve <NUM> and friction pin <NUM> rotating within the clamp <NUM>. A spindle <NUM> that is coupled to the friction sleeve <NUM> and friction pin <NUM> rotates the sleeve and pin about a rotational axis R of the spindle. The tool <NUM> locally heats the workpieces <NUM>, <NUM> to a plastic state. The friction sleeve <NUM> is then pushed into the workpieces <NUM>, <NUM> to a desired depth within the lower workpiece <NUM>, while the friction pin <NUM> is retracted away from the workpieces. The spindle <NUM> has separate axially-movable portions that drive the friction sleeve <NUM> and friction pin <NUM> to rotate and translate axially. Material from the workpieces <NUM>, <NUM> is displaced upward into the volume created by the movement of the friction sleeve <NUM> and the friction pin <NUM>. The plastic material from the workpieces <NUM>, <NUM> is stirred together, and the friction sleeve <NUM> and friction pin <NUM> are returned to their initial flush condition to force the displaced plastic material back toward the workpieces, thereby forming a generally flush spot weld <NUM>. The tool <NUM> and anvil <NUM> are then separated, while the workpieces <NUM>, <NUM> remain joined by the spot weld <NUM>. The refill friction stir spot welding process is quick, e.g., less than <NUM> seconds (depending on the thickness of the workpieces). Although the friction sleeve <NUM> is shown as being pushed into the workpieces <NUM>, <NUM> and the friction pin <NUM> retracted, it is to be appreciated that the friction pin can alternatively be pushed into the workpieces and the friction sleeve retracted during the refill friction stir spot welding process.

As noted above, refill friction stir spot welding tools can become clogged, worn, etc. over time and must be replaced. Replacing refill friction stir spot welding tools is labor-intensive and time-consuming, and, thus, can be expensive and can lead to undesirable down time. Conventional refill friction stir spot welding tools are held in place by various separate fasteners (e.g., bolts, union nuts, etc.) that must be removed and remounted to replace the tool. It can typically take as long as <NUM> minutes to replace conventional refill friction stir spot welding tools.

<FIG> shows a robot arm <NUM> to which a refill friction stir spot welding end effector <NUM> is mounted. The end effector <NUM> includes the refill friction stir spot welding tool <NUM>. The tool <NUM> is attached to a weld head <NUM> on the end effector <NUM> that includes the spindle for driving the tool. The refill friction stir spot welding tool <NUM> has a quick connect attachment structure, discussed below, to allow the tool to be switched out or replaced quickly, such as within two minutes instead of <NUM> minutes.

The end effector <NUM> can include an anvil arm <NUM> that holds the anvil <NUM>. The anvil arm <NUM> supports the anvil <NUM> such that the anvil is aligned with the clamp <NUM>, friction sleeve and friction pin of the tool <NUM> along the rotational axis R (<FIG>) of the tool. The anvil arm <NUM> can have a curved shape and forms a lower jaw of the end effector <NUM>, so that the end effector has a generally C-shaped appearance. In certain embodiments, the anvil <NUM> is not attached to an end effector <NUM>, but is separate from the weld head. For example, in a gantry-style machine, the refill friction stir spot welding tool can be mounted to a weld head that is attached to a gantry, for horizontal and vertical movements, and the anvil can be attached to a movable table or other lower fixture tooling. A pedestal-style machine could also have an anvil mounted to lower fixture tooling separate from the weld head.

The end effector <NUM> can include various motors, such as servo motors, to control the operation of a spindle that rotates the friction sleeve and friction pin about the rotational axis R (<FIG>) and control the axial movement of the sleeve and pin during welding. For example, the end effector <NUM> can include three separate servo motors that respectively drive the rotation of the spindle and the independent linear axial movements of the friction sleeve and friction pin. The servo motor <NUM> on the weld head <NUM> that rotates the spindle, and the servo motor <NUM> that linearly (axially) drives the friction sleeve, can be seen in <FIG>. A servo motor similar to the servo motor <NUM> for the friction sleeve can be located on the opposite side of the end effector <NUM> for linearly (axially) driving the friction pin. The end effector <NUM> can further include a servo motor that opens and closes the upper and lower "jaws" of the end effector <NUM>, to clamp the workpieces between the clamp <NUM> and the anvil <NUM>. It is to be appreciated that the anvil <NUM> and anvil arm <NUM> can be driven upward toward the clamp <NUM> or the clamp <NUM> and upper structure of the end effector <NUM> can be driven downward toward the anvil <NUM>.

The end effector <NUM> includes a clamp receiver <NUM> for holding the clamp <NUM>. The friction sleeve and the friction pin are attached directly to the spindle of the end effector <NUM>. The spindle can have an outer portion and an inner portion to which the friction sleeve and friction pin are respectively attached. The outer and inner portions of the spindle rotate and can move linearly (axially) independently from one another during the refill friction stir spot welding process. The tool <NUM>, clamp receiver <NUM> and spindle provide the quick connect attachment structures discussed below, to allow the tool to be switched out or replaced quickly.

<FIG> show the refill friction stir spot welding tool <NUM> in further detail. The clamp <NUM> can have a two-piece design comprising a lower clamp and an upper clamp holder <NUM>, which gets attached to the clamp receiver on the end effector. The lower clamp can be bolted to the clamp holder <NUM> as shown, or attached to the clamp holder in another manner (e.g., screwed onto the clamp holder). A two-piece design can allow the lower clamp to be replaced if it becomes worn or damaged. Alternatively, the clamp <NUM> can have a one-piece design in which the lower clamp and clamp holder <NUM> are monolithically formed. The clamp holder <NUM> can include surface features, such as flats <NUM>, that facilitate handling of the clamp and/or properly locating the clamp, such as within a tool storage receptacle.

At the top of the clamp holder <NUM> are a series of radially-projecting mounting tabs <NUM>. The radially-projecting mounting tabs <NUM> engage mounting slots in the clamp receiver located on the end effector, to provide the quick connect/disconnect functionality of the clamp <NUM>. In the embodiment shown in the drawings, the clamp holder <NUM> has four radially-projecting mounting tabs <NUM> symmetrically spaced at <NUM>° intervals around the circumference of the clamp holder. However, it is to be appreciated that the clamp holder <NUM> can include fewer or more than four radially-projecting mounting tabs <NUM> and that the mounting tabs need not be symmetrically spaced around the clamp holder. The clamp <NUM> is attachable to and detachable from the clamp receiver on the end effector by rotations of the clamp through less than <NUM>°. For example, the clamp <NUM> can be rotated clockwise through less than <NUM>° to attach the clamp, and rotated counterclockwise through less than <NUM>° to detach the clamp (or vice versa). In certain embodiments, the clamp <NUM> is attachable to and detachable from the clamp receiver by rotations of the clamp relative to the clamp receiver through less than <NUM>°, such as via a quarter turn (<NUM>°) or less of the clamp. <FIG> shows the clamp <NUM> separate from the friction sleeve <NUM> and friction pin <NUM>.

With reference to <FIG>, the friction sleeve <NUM> is located within the clamp <NUM> and is coaxially aligned with the clamp. The friction sleeve <NUM> also has radially-projecting mounting tabs <NUM>. The radially-projecting mounting tabs <NUM> on the friction sleeve <NUM> engage mounting slots on the spindle of the end effector, to provide the quick connect/disconnect functionality of the friction sleeve. In the embodiment shown in the drawings, the friction sleeve <NUM> has four radially-projecting mounting tabs <NUM> symmetrically spaced at <NUM>° intervals around the circumference of the friction sleeve. However, it is to be appreciated that the friction sleeve <NUM> can include fewer or more than four radially-projecting mounting tabs <NUM> and that the mounting tabs need not be symmetrically spaced around the friction sleeve. The friction sleeve <NUM> can have a different number of radially-projecting mounting tabs than the clamp <NUM>, and the shape and/or configuration of the mounting tabs <NUM> on the friction sleeve <NUM> can differ from the mounting tabs <NUM> on the clamp <NUM>. The friction sleeve <NUM> is attachable to and detachable from the spindle on the end effector by rotations of the friction sleeve through less than <NUM>°. For example, the friction sleeve <NUM> can be rotated clockwise through less than <NUM>° to attach the friction sleeve, and rotated counterclockwise through less than <NUM>° to detach the friction sleeve (or vice versa). In certain embodiments, the friction sleeve <NUM> is attachable to and detachable from the spindle on the end effector by rotations of the friction sleeve relative to the spindle through less than <NUM>°, such as via a quarter turn (<NUM>°) or less of the friction sleeve. It can be seen that the radially-projecting mounting tabs <NUM> on the friction sleeve <NUM> are located at a different axial location along the rotational axis R of the tool <NUM> than the radially-projecting mounting tabs <NUM> on the clamp <NUM>. For example, the radially-projecting mounting tabs <NUM> on the friction sleeve <NUM> are located higher along the axis R of the tool <NUM> than the mounting tabs <NUM> on the clamp <NUM>. The radially-projecting mounting tabs <NUM> on the friction sleeve <NUM> are also located radially inward of the mounting tabs <NUM> on the clamp <NUM>.

<FIG> shows the friction sleeve <NUM> separate from the clamp <NUM> and friction pin <NUM>. The friction sleeve <NUM> can have a two-piece design comprising a lower sleeve <NUM> and an upper sleeve holder <NUM>. The sleeve holder <NUM> includes the radially-projecting mounting tabs <NUM> and will be attached to the spindle on the end effector. The lower sleeve <NUM> can be threaded into the sleeve holder <NUM>, or attached to the sleeve holder in another fashion. A two-piece design can allow the lower sleeve <NUM> to be replaced if it becomes worn or damaged. Alternatively, the friction sleeve <NUM> can have a one-piece design in which the lower sleeve <NUM> and sleeve holder <NUM> are monolithically formed. The upper sleeve holder <NUM> has a larger diameter than the lower sleeve <NUM>. The upper sleeve holder <NUM> can include surface features, such as flats <NUM>, that facilitate handling of the friction sleeve <NUM> and/or properly locating the friction sleeve, such as within a tool storage receptacle. The lower sleeve <NUM> can also include surface features, such as flats <NUM>, that can help a tool grip the lower sleeve when it is threaded into the upper sleeve holder <NUM>.

With reference to <FIG> and <FIG>, the friction pin <NUM> is located within the friction sleeve <NUM> and, thus, within the clamp <NUM>. The friction pin <NUM> is coaxially aligned with the clamp <NUM> and the friction sleeve <NUM> along the rotational axis R of the tool <NUM>. In the embodiment shown, the friction pin <NUM> has a stadium-shaped or obround mounting head <NUM> located at the proximal or top end of the pin. For example, the central portion of the mounting head <NUM> having longer sides is rectangular, and the shorter ends of the mounting head are semicircular when viewed axially along the friction pin <NUM>. The stadium shape of the mounting head <NUM> matches a similarly-shaped opening or mounting slot in the inner portion of the spindle. The stadium-shaped mounting head <NUM> is attached to the main body of the friction pin <NUM> by a short neck portion <NUM>. The friction pin <NUM> is captured by the inner portion of the spindle via the neck portion <NUM> and, prior to clamping/welding workpieces, is suspended from the spindle by the stadium-shaped mounting head <NUM>. It is to be appreciated that the mounting head <NUM> could have various shapes, such as a rectangular shape for example.

The friction pin <NUM> is attachable to and detachable from the spindle on the end effector by rotations of the friction pin through less than <NUM>°. For example, the friction pin <NUM> can be rotated clockwise through less than <NUM>° to attach the friction pin, and rotated counterclockwise through less than <NUM>° to detach the friction pin (or vice versa). In certain embodiments, the friction pin <NUM> is attachable to and detachable from the spindle by rotations of the friction pin relative to the spindle through less than <NUM>°, such as via a quarter turn (<NUM>°) or less of the friction pin. It can be seen that the stadium-shaped mounting head <NUM> on the friction pin <NUM> is located at a different axial location along the rotational axis R of the tool <NUM> than the radially-projecting mounting tabs on the clamp <NUM> and friction sleeve <NUM>. For example, the stadium-shaped mounting head <NUM> is located higher along the axis R of the tool <NUM> than the mounting tabs <NUM>, <NUM> on the clamp <NUM> and friction sleeve <NUM>. The stadium-shaped mounting head <NUM> is also located radially inward of the mounting tabs <NUM>, <NUM> on the clamp <NUM> and friction sleeve <NUM>.

It can be seen in <FIG> and <FIG> that the friction pin <NUM> is longer than the friction sleeve <NUM>, and that the friction sleeve is longer than the clamp <NUM>. In certain embodiments, the refill friction stir spot welding tool <NUM> is water cooled. The clamp holder <NUM> can include sealed water apertures or fittings <NUM> (<FIG>) for conveying cooling water received from the end effector.

<FIG> provides a perspective view of a portion of the end effector <NUM> looking toward the distal end of the refill friction stir spot welding tool <NUM>. The friction sleeve <NUM> and friction pin <NUM> can be seen flush with the distal end of the clamp <NUM>. The clamp holder <NUM> is attached to the clamp receiver <NUM> on the end effector <NUM> via mounting slots <NUM> on the clamp receiver.

<FIG> and <FIG> show the clamp receiver <NUM> and spindle of end effector's weld head. The spindle has an outer portion <NUM> that holds and drives the friction sleeve, and an inner portion <NUM> that holds and drives the friction pin. The portions <NUM>, <NUM> of the spindle rotate in the same direction during refill friction stir spot welding; however, they are independently linearly movable back and forth along the rotational axis of the spindle by servo motors on the end effector. The inner portion <NUM> of the spindle has a stadium-shaped slot <NUM> for receiving the stadium-shaped mounting head of the friction pin. The mounting head of the friction pin is inserted into the stadium-shaped slot <NUM> and the pin is rotated and captured around its neck portion. The outer portion <NUM> of the spindle has mounting slots <NUM> for receiving the radially-projecting tabs on the friction sleeve. There are an equal number of mounting slots <NUM> as there are mounting tabs on the friction sleeve. The mounting slots <NUM> have an axial portion that leads to a circumferential portion, so that the friction sleeve can be inserted axially into the outer portion <NUM> of the spindle and rotated relative to the spindle. Prior to performing a welding operation, the friction sleeve is suspended from the spindle via its mounting tabs resting on the circumferential portions of the mounting slots <NUM>. The spindle rotates in one direction, which serves to keep the friction sleeve and friction pin in place without an additional locking mechanism. However, if desired, such a locking mechanism can be provided (e.g., a selectively deployable pin, such as a shot pin). The circumferential portion of the slot <NUM> can include a mechanical stop to limit the rotation of the friction sleeve relative to the spindle.

The clamp receiver <NUM> also has mounting slots <NUM> having an axial portion that leads to a circumferential portion, so that the clamp can be inserted axially into the clamp receiver <NUM> and rotated relative to the clamp receiver. The circumferential portion of the slot can be in the form of a shelf that supports the clamp via the clamp's radially-projecting mounting tabs. The circumferential portion of the slot <NUM> can include mechanical stops to limit the rotation of the clamp relative to the clamp receiver <NUM>. There are an equal number of mounting slots <NUM> as there are mounting tabs on the clamp. The clamp receiver <NUM> does not rotate. To help lock the clamp in place, the end effector can include a locking mechanism <NUM> (e.g., a selectively deployable pin, such as a shot pin) that prevents the clamp from rotating or backing out of the mounting slots <NUM> once in place. The locking mechanism <NUM> can also help to rotationally orient the clamp and/or the friction sleeve within the weld head.

In certain embodiments, the friction pin, friction sleeve and clamp can be provided together as a kit, either as an assembled tool or as separate components for later assembly. In certain embodiments, the friction pin, friction sleeve and clamp can be installed on the weld head simultaneously. The friction pin, friction sleeve and clamp can also be installed one at a time, e.g., with the friction sleeve slid over the alreadymounted friction pin, and the clamp then installed over the friction sleeve. The friction pin, friction sleeve and clamp can be installed manually or automatically by the robot arm. Although a tab-and-slot quick connect mounting system has been described above, it is to be appreciated that other quick connect mounting systems could be employed on a refill friction stir spot welding tool. For example, ball lock quick connects could be provided for attaching/detaching the friction pin, the friction sleeve and/or the clamp to the end effector. Ball lock quick connects could include biased captive balls within the weld head that are radially movable to capture the components of the refill friction stir spot welding tool as the components are axially translated relative to the weld head. For example, the captive balls could engage concave slots on the tool components to attach them to the weld head.

The quick connect refill friction stir spot welding tool has been discussed above in detail in the context of an end effector mounted to a robot arm. However, it is to be appreciated that the quick connect tool could also be used in other types of refill friction stir spot machines, such as gantry-style machines and pedestal-style machines for example.

Claim 1:
A quick connect refill friction stir spot welding tool (<NUM>), comprising:
a clamp (<NUM>);
a friction sleeve (<NUM>) located coaxially within the clamp (<NUM>);
a friction pin (<NUM>) located coaxially within the clamp (<NUM>) and friction sleeve (<NUM>); and
characterized by:
wherein the clamp (<NUM>) comprises a first radially-projecting mounting tab (<NUM>) configured for engaging a first mounting slot (<NUM>) in a clamp receiver (<NUM>) of a refill friction stir spot welding weld head (<NUM>);
wherein the friction sleeve (<NUM>) comprises a second radially-projecting mounting tab (<NUM>) configured for engaging a second mounting slot (<NUM>) in a spindle (<NUM>) of the refill friction stir spot welding weld head (<NUM>), wherein the second radially-projecting mounting tab (<NUM>) is
located at a different axial location along an axis of the tool (<NUM>) than the first radially-projecting mounting tab (<NUM>), and radially inward thereof; and
wherein the clamp (<NUM>) is attachable to and detachable from the refill friction stir spot welding weld head (<NUM>) by rotations of the clamp (<NUM>) through less than <NUM> degrees, and
wherein the friction sleeve (<NUM>) is attachable to and detachable from the refill friction stir spot welding weld head (<NUM>) by rotations of the friction sleeve (<NUM>) through less than <NUM> degrees.