Axially and radially compliant deburring tool

An axially and radially compliant deburring tool holds a commercially available end tool holder, which in turn holds a variety of commercially available interchangeable deburring end tools, such as those commercially available for the hand deburring market. The axially and radially compliant deburring tool exhibits axial compliance in response to an external force by allowing a longitudinal sleeve holding the end tool holder to move longitudinally along a longitudinal axis of the tool, against a bias force. The axially and radially compliant deburring tool exhibits radial compliance in response to an external force by interaction between a cam contact member and a concave cam surface, both under the bias force and hence operative to return the commercially available to a centered, extended position in the absence of external forces.

FIELD OF INVENTION

The present invention relates generally to deburring tools for automated equipment and in particular to an axially and radially compliant deburring tool operative to accept interchangeable deburring end tools commercially available in the hand deburring market.

BACKGROUND

Industrial robots and related automated equipment, such as Computer Numeric Controlled (CNC) machines, are a common and indispensable part of modern manufacturing. Automated equipment performs routine and repetitive tasks tirelessly, in hostile environments, and with high precision and repeatability. Such tasks include the deburring of the edges of machined or cast parts, or the related task of cutting away material from injection molded or blow-molded parts. Conventionally, the deburring or trimming has been done by hand. It is known to use a robotic arm fitted with a deburring or cutting tool and programmed to follow a path around the edge of a particular part or object which is to be deburred or trimmed. As used herein, the term “deburring” is to be construed broadly, to include grinding, filing, polishing, cutting, trimming, and similar finishing operations.

There are some difficulties normally associated with the use of automatically controlled deburring tools. Since the programmed path of a robotic arm is in essence a series of incremental steps, the path of the automatically controlled deburring tool may not exactly coincide with the shape or contours of the surface to be deburred. In addition, the edge or surface of a workpiece may have cavities or protrusions, which interfere with the path and cutting force of the robotic tool. A protrusion will urge the cutting surface of the deburring tool out of its programmed path and cause a consequent increase in cutting force. The increased cutting force may cause the deburring tool to cut too deep into the surface. Moreover, the increased cutting force may cause damage to the cutting surface of the tool. A cavity on the other hand may cause the deburring tool to separate or diverge from the surface to be deburred. The separation of the cutting surface of the tool from the surface to be deburred will prevent the deburring of that portion of the part or workpiece. Consequently, the overall quality of the product being deburred will be affected.

In addition to part variations, there are fixture variations. Fixtures are structures that hold the parts while the parts are being subjected to deburring. Fixtures are designed to hold the parts such that the surface to be deburred aligns with the programmed path of the deburring tool. However, typically, these fixtures will have variations, and the variations will result in the surfaces of the parts to be deburred being misaligned with the programmed path of the deburring tool.

Due to these known problems with automated deburring operations, many deburring tasks are performed manually. Unlike robots, humans receive both visual cues and tactile feedback, and accommodate surface imperfections and misaligned fixtures as a matter of course. However, overcoming the problems associated with automated deburring would bring the known benefits of automation, such as speed, accuracy, precision, repeatability, tirelessness, and operation in hostile environments, to the deburring operation.

One approach to addressing these problems is compliance in the automated deburring tool. Compliance compensates for errors in the path and variations in parts and fixtures by permitting limited movement of the tool while maintaining an acceptable cutting force. In this way, variations in the surface being deburred, or inaccuracies in the programmed path which are within the limits of the compliance, will be accommodated and damage to the cutting surface of the tool and the finished product will be minimized.

The Background section of this document is provided to place embodiments of the present invention in technological and operational context, to assist those of skill in the art in understanding their scope and utility. Unless explicitly identified as such, no statement herein is admitted to be prior art merely by its inclusion in the Background section.

SUMMARY

The following presents a simplified summary of the disclosure in order to provide a basic understanding to those of skill in the art. This summary is not an extensive overview of the disclosure and is not intended to identify key/critical elements of embodiments of the invention or to delineate the scope of the invention. The sole purpose of this summary is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

According to embodiments of the present invention described and claimed herein, an axially and radially compliant deburring tool holds a commercially available end tool holder, which in turn holds a variety of commercially available interchangeable deburring end tools, such as those commercially available for the hand deburring market. The axially and radially compliant deburring tool exhibits axial compliance in response to an external force by allowing a longitudinal sleeve holding the end tool holder to move longitudinally along a longitudinal axis of the tool, against a bias force. The axially and radially compliant deburring tool exhibits radial compliance in response to an external force by interaction between a cam contact member and a concave cam surface, both under the bias force and hence operative to return the commercially available to a centered, extended position in the absence of external forces.

One embodiment relates to an axially and radially compliant deburring tool. The deburring tool includes a housing having a longitudinal axis and a longitudinal sleeve operative to hold an end tool holder, which is operative to hold an interchangeable deburring end tool. The deburring tool also includes a pivoting sleeve operative to slideably hold the longitudinal sleeve, and a pivoting suspension connecting the pivoting sleeve to the front of the housing. The pivoting suspension is operative to allow the pivoting sleeve to pivot about the longitudinal axis in all radial directions. The deburring tool further includes a cam contact member and a cam block including a concave cam surface. One of the cam contact member and cam block is affixed to the longitudinal sleeve. The other of the cam contact member and cam block is slideably mounted within the housing, and biased away from a back of the housing. This element is operative to provide axial compliance by moving along the longitudinal axis in response to an external axial force exerted on the longitudinal sleeve. The element is also operative to provide radial compliance by moving along the longitudinal axis in response to interaction between the cam contact member and the concave cam surface as the longitudinal sleeve pivots from alignment with the longitudinal axis under an external force.

DETAILED DESCRIPTION

For simplicity and illustrative purposes, the present invention is described by referring mainly to an exemplary embodiment thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be readily apparent to one of ordinary skill in the art that the present invention may be practiced without limitation to these specific details. In this description, well known methods and structures have not been described in detail so as not to unnecessarily obscure the present invention.

As mentioned above, deburring is typically a manual operation. Accordingly, a wide variety of interchangeable deburring end tools, and end tool holders that facilitate their mounting within a handle, are made for hand deburring operations, and are commercially available. One example of commercially available deburring end tools is the SHAVIV line of deburring blades and scrapers available from VARGUS of Nahariya, Israel. Another are the blades, countersinks, scrapers, cutting and ceramic tools available for the NOGA deburring tools, available from Noga Engineering, Inc. of Shlomi, Israel. These deburring blades, scrapers, and the like come in a wide variety of shapes and sizes. They generally include a tool (blade, scraper, etc.) that is inserted into an end tool holder. The end tool holder comprises a shaft having ridges formed in one flattened surface thereof. The end tool holder is designed to be removeably inserted into deburring tool handles, and is held securely in such handles by various detent mechanisms, which engage the ridges formed on the shaft of the end tool holder. According to embodiments of the present invention, a radially and axially compliant deburring tool, which may be operated by a robotic arm, a CNC machine, or other automated equipment, is designed to accept and utilize the vast array of interchangeable deburring end tools, together with their end tool holders, which are available in the hand deburring market. This increases the flexibility of the radially and axially compliant deburring tool, and increases the number of applications for which it may be advantageously employed.

FIG. 1depicts a first embodiment of an axially and radially compliant deburring tool10. The deburring tool10comprises a housing12, into which is asserted a commercially available end tool holder18. In this embodiment, the housing12is generally cylindrical, although this shape is not limiting. The housing12has a front14and a back16. The end tool holder18partially extends from the front14of the housing12. The end tool holder18is operative to hold an interchangeable deburring end tool, which is inserted in a central bore20in the end tool holder18. The end tool holder18(and bore20), in the default position depicted inFIG. 1, is aligned with a longitudinal axis22of the robotic deburring tool10.

As mentioned above, to increase the utility and amortize the cost of the axially and radially compliant deburring tool10, a bore20in the end tool holder18is sized and shaped to accept the shafts of a wide variety of commercially available interchangeable deburring end tools. In one embodiment, the deburring tool10includes a detent-based end tool locking mechanism24operative to securely hold an end tool holder18. The detent-based end tool locking mechanism24allows the end tool holder18to be positioned at a variety of positions along the longitudinal axis22.

To facilitate deburring operations on parts having protruding parts or recess, fixtures having imprecise shape or alignment, and/or similar problems with automated deburring operations, the end tool holder18is compliant with respect to the housing12in both axial and radial directions.

As used herein, axial compliance means the end tool holder18is operative to move, along the longitudinal axis22, toward the back16of the housing12, under an external force applied to an interchangeable deburring end tool secured in the end tool holder18. The external force may include the force exerted on the interchangeable deburring end tool by a workpiece in response to a robot or other automated equipment moving the robotic deburring tool10towards and into contact with the workpiece. Upon the removal of the external force, the end tool holder18will return to its partially extended position with respect to the housing12, also referred to herein as a default position, as depicted inFIG. 2.

FIG. 2depicts a section view of the first embodiment of the axially and radially compliant deburring tool10ofFIG. 1. Axial compliance is accomplished by interaction of the end tool holder18, longitudinal sleeve21, cam contact member26, cam block28, bias spring30, and spring force adjustment cup32. The end tool holder18is disposed within a longitudinal sleeve21. The longitudinal sleeve21, containing the end tool holder18, is slideably mounted within a pivoting sleeve36. This allows the longitudinal sleeve21, and hence the end tool holder18, to move along the longitudinal axis22. The cam contact member26is held by a cam contact member holding block34, which is affixed to the back of the longitudinal sleeve21. The forward-most, default position of the longitudinal sleeve21, and hence the end tool holder18, is defined by the cam contact member holding block34contacting the pivoting sleeve36.

The cam contact member26contacts a cam block28, which is slideably mounted within the housing12and operative to move along the longitudinal axis22. The cam block28is biased toward the front14of the housing12by a bias force, provided (in the embodiment shown) by a bias spring30. In other embodiments, the bias force may be provided by a pneumatically or hydraulically driven piston, a solenoid, a voice coil, pneumatic artificial muscles (PAM), or other axial force producing mechanism, as known in the art. In the embodiment depicted, the bias spring30is seated, towards the back16of the housing12, in a spring force adjustment cup32. At the other end, the bias spring30is seated against a flange38formed on the cam block28.

FIG. 3depicts the axially and radially compliant deburring tool10under full axial compliance, wherein an external force deflects the end tool holder18into the housing12, against the force of the bias spring30. The bias spring30is compressed, and the cam block28, cam contact member26, cam contact member holding block34, and longitudinal sleeve21holding the end tool holder18, are all displaced, from their default position, towards the rear16of the housing12.

In one embodiment, the axial compliance force is at least partially adjustable. In particular, in the embodiment depicted, the outer surface of the spring force adjustment cup32is threaded, and a corresponding portion of the inner surface of the housing12is threaded. A hex (or other shaped) receptacle33in the back of the spring force adjustment cup32accepts a corresponding tool inserted through a bore40in the housing12, to rotate the spring force adjustment cup32. This adjusts the “preload” force on the bias spring30by changing the axial position of the spring force adjustment cup32within the housing12. Those of skill in the art will readily recognize that other bias force adjustment mechanisms are possible within the scope of the present invention.

As used herein, radial compliance means the end tool holder18is operative to pivot from alignment with the longitudinal axis22, in any radial direction, under an external force applied to an interchangeable deburring end tool secured in the end tool holder18. The external force may include the force exerted on the axially and radially compliant deburring tool10by a workpiece in response to a robot or other automated equipment moving the axially and radially compliant deburring tool10against the workpiece. Upon the removal of the external force, the end tool holder18will return to its centered position with respect to the housing12, also referred to herein as the default position—that is, aligned with the longitudinal axis22—as depicted inFIG. 2.

FIG. 4depicts the axially and radially compliant deburring tool10under full radial compliance, wherein an external force deflects the end tool holder18to the side, causing it and the longitudinal sleeve21to pivot out of alignment with the longitudinal axis22. The pivoting sleeve36is connected to the housing12at the front14thereof by a pivoting suspension42. The pivoting suspension42allows the pivoting sleeve36(and hence longitudinal sleeve21and end tool holder18) to pivot in any radial direction. In one embodiment, the pivoting suspension42comprises a two-axis gimbal, although this is not limiting.

As an interchangeable deburring end tool, and hence the front of the end tool holder18, is deflected in a radial direction, the cam contact member26, attached to the back of the longitudinal sleeve21, is deflected within the housing12in the opposite radial direction. The cam block28includes a concave cam surface44formed in the front thereof, facing the cam contact member26. Interaction between the cam contact member26and the concave cam surface44, under radial compliance, displaces the cam block28toward the back16of the housing12, against the bias force, such as that provided by the bias spring30. That is, the cam contact member26acts similarly to a cam follower, except that, upon the application of an external deflecting force, the cam contact member26displaces the cam block28, according to the shape of the concave cam surface44, rather than being driven by it. When the external force is removed, the bias force and interaction between the cam contact member26and the concave cam surface44act to center the cam contact member26at the center of the concave cam surface44, thus returning the longitudinal sleeve21, and hence the end tool holder18, to the centered, or default, position—that is, aligned with the longitudinal axis22—as depicted inFIG. 2. During this recovery—returning the deburring tool10to its default position following the removal of an external deflecting force—the cam contact member26acts as a traditional cam follower in its interaction with the concave cam surface44.

In the embodiment depicted inFIGS. 2 and 4, the concave cam surface44is substantially conical. In one embodiment, the angle of the substantially conical cam surface44is approximately 45°. However, other angles—and indeed, other shapes—for the concave cam surface44are contemplated within the scope of the present invention. In general, for a given deflection of the end tool holder18, a steeper angle of the cam surface44will require a greater axial displacement of the cam block28, which will present a “stiffer” compliance as greater force will be required to overcome the bias force. Conversely, a shallower angle of the cam surface44will present a lower compliance force. The concave cam surface44may also assume a non-conical shape, such as hemispherical, parabolic, or other concave shape. For example, in some embodiments in may be desirable to alter the radial compliance force as a function of the degree of compliance (i.e., the degree of displacement of the end tool18from alignment with the longitudinal axis22). This may be accomplished by altering the angle of the concave cam surface44as a function of the distance from the center of the cam block28.

Similarly, the cam contact member26is not, in general, limited to a spherical shape, as depicted. Rather, the cam contact member26may assume any shape that, in any given configuration of deburring tool10, provides the optimal compliance force and resetting operation.

Although described separately herein for clarity of explanation, axial and radial compliance may occur simultaneously.FIG. 5depicts the axially and radially compliant deburring tool10undergoing both axial and radial compliance. The cam block28is displaced slightly toward the rear16of the housing12by interaction between the cam contact member26and concave cam surface44under radial compliance. However, the cam block28is also further displaced toward the rear16under radial compliance. Upon removal of all external forces, the bias force provided by, e.g., the bias spring30, will act to return the axially and radially compliant deburring tool10to its default position, with the bit holder18both centered, in alignment with the longitudinal axis18, and extended to its forward-most position, as depicted inFIG. 2.

FIG. 6depicts a second embodiment of an axially and radially compliant deburring tool10. In this embodiment, the relative positions of the cam block28with a concave cam surface44, and the cam contact member26, are reversed. That is, the cam block28is affixed to the back of the end tool holder18, with the concave cam surface44facing the back16of the housing12. The cam contact member26, which faces the front14of the housing12, so as to contact the concave cam surface44, is affixed to a plunger46. The plunger46is slideably mounted in a bore48in the back16of the housing12. The plunger46and cam contact member26are biased toward the front14of the housing12by the bias spring30. Under both axial and radial compliance, the axially and radially compliant deburring tool10according to the second embodiment operates substantially as described above for the first embodiment, but with the cam contact member26and plunger46moving axially within the housing12rather than the cam block28. Additionally, and oppositely to the first embodiment described above (FIGS. 2-5), during compliance, the cam contact member26acts as a cam follower, being driven by motion of the concave cam surface44of the cam block28. During recovery—that is, returning the deburring tool10to its default position with the end tool holder18centered on the longitudinal axis22and extended to a forward position—the cam contact member26drives the cam block28.FIG. 6also depicts an interchangeable deburring end tool50—in this case, having a blade—inserted in the end tool holder18.

Embodiments of the present invention present numerous advantages over prior art deburring tools. By providing both axial and radial compliance, the deburring tool10may find application in automatically deburring, cutting, trimming, dressing, polishing, and otherwise finishing a variety of workpieces, which tasks are currently performed by hand. By configuring the end tool holder18to hold commercially available interchangeable deburring end tools made for the hand deburring market, a very large array of end tools are available, to address virtually any deburring application. The flexibility and versatility of the axially and radially compliant deburring tool10is further enhanced by providing for control over the axial and radial compliance forces, such as by adjusting the compression of the bias spring30, and/or altering the shape of the concave cam surface44.