MAGNETICALLY ACTUATED ROLLER HEAD

Abstract

A magnetically actuated roller head includes a linear actuator mountable on an end of a multi-axis robotic arm. The linear actuator includes a slide, a magnet operably connected to the slide and operable to urge the slide in a linear direction, and a connector disposed on a distal end of the slide. A roller hemming head is mounted on the linear actuator by the connector. The roller hemming head includes at least one hem roller.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority of U.S. Provisional Application No. 61/070,551 filed Mar. 24, 2008.

TECHNICAL FIELD

This invention relates to robotic roller hemming, and more particularly a robotic roller head used for robotic roller hemming such as hemming of vehicle closure panels.

BACKGROUND OF THE INVENTION

It is known in the art relating to actuation of a roller hemming head that conventional actuators typically require one or more of the following: hydraulics, pneumatics, electric cylinders, gas spring charge, monitoring of air or gas pressure, and oil disposal. These requirements may elevate the cost, size, and complexity of a conventional roller hemming head.

SUMMARY OF THE INVENTION

The present invention provides a magnetically actuated roller hemming head that utilizes magnetic and/or electromagnetic force to actuate a roller hemming head and to provide a hemming force through a hem roller of the roller hemming head. The present invention may allow for variable force control on the roller head with instantaneous response time to roller head force changes. The present invention also may eliminate the need for some or all of the following: hydraulics, pneumatics, electric cylinders, gas spring charge, monitoring of air or gas pressure, and oil disposal.

More particularly, a magnetically actuated roller head in accordance with the present invention includes a linear actuator mountable on an end of a multi-axis robotic arm. The linear actuator includes a slide, a magnet operably connected to the slide and operable to urge the slide in a linear direction, and a connector disposed on a distal end of the slide. A roller hemming head is mounted on the linear actuator by the connector. The roller hemming head includes at least one hem roller.

Optionally, the magnet may be a rare earth magnet. Alternatively, the linear actuator may include a rare earth magnet disposed between two opposing magnets. The polarity of one of the opposing magnets may be disposed in the same direction as the polarity of the rare earth magnet, and the polarity of the other of the opposing magnets may be disposed in an opposite direction to the polarity of the rare earth magnet. Optionally, the two opposing magnets may be rare earth magnets. Alternatively, the linear actuator may include an electromagnet disposed on each of opposite sides of the magnet. The electromagnets control and assist a force transmitted by the magnet.

Also, the slide may include an anti-rotate feature.

In another embodiment, a magnetically actuated roller head includes a housing having an internal bore. The housing is mountable on an end of a multi-axis robotic arm. A pair of opposing actuator members are fixedly mounted within the inner bore. A shaft extends through the actuator members. A magnet is mounted on the shaft and is moveable within the inner bore. The magnet is disposed between the actuator members. A slide is connected to the shaft and extends outwardly from the housing. A connector is disposed on a distal end of the slide. A roller hemming head is mounted on the connector. The roller hemming head includes at least one hem roller. The actuator members control and assist a hemming force applied by the roller hemming head through the magnet.

Optionally, the magnet may be a rare earth magnet. Also, the actuator members may be rare earth magnets. The polarity of one of the actuator members may be disposed in the same direction as the polarity of the rare earth magnet, and the polarity of the other of the actuator members may be disposed in an opposite direction to the polarity of the rare earth magnet. Alternatively, the actuator members may be electromagnets.

The housing may include an anti-rotate linear guide, and the slide may include an anti-rotate feature cooperable with the linear guide. The anti-rotate feature may be one of a spline, a ball spline, and a square linear bearing.

A method of roller hemming in accordance with the present invention includes mounting a linear actuator on an end of a multi-axis robotic arm, the linear actuator including a slide, a magnet operably connected to the slide and operable to urge the slide in a linear direction, and a connector disposed on a distal end of the slide; and mounting a roller hemming head on the linear actuator by the connector, the roller hemming head including at least one hem roller. The linear actuator provides a hemming force for performing roller hemming operations with the hem roller.

Optionally, the magnet may be a rare earth magnet. The method may also include disposing the magnet between a pair of opposing actuator members. The actuator members may be rare earth magnets. Alternatively, the actuator members may be electromagnets.

The method may also include restricting axial rotation of the roller hemming head by providing a spline on the slide. Also, the method may include providing a plurality of different hem rollers on the roller hemming head.

These and other features and advantages of the invention will be more fully understood from the following detailed description of the invention taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a sectional view of a magnetically actuated roller head in accordance with a first embodiment of the present invention;

FIG. 2 is a sectional view of a magnetically actuated roller head in accordance with a second embodiment of the present invention for push type roller hemming;

FIG. 3 is a sectional view of a magnetically actuated roller head similar to the embodiment of FIG. 2 for pull type roller hemming;

FIG. 4 is a sectional view of a magnetically actuated roller head in accordance with a third embodiment of the present invention for push type roller hemming; and

FIG. 5 is a sectional view of a magnetically actuated roller head similar to the embodiment of FIG. 4 for pull type roller hemming.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings in detail, numeral 110 generally indicates a magnetically actuated roller head in accordance with the present invention. The magnetically actuated roller head utilizes magnetic and/or electromagnetic force to actuate a roller hemming head and to provide a hemming force through a hem roller of the roller hemming head.

With reference to FIG. 1, in a first embodiment the magnetically actuated roller head 110 includes a linear actuator 112 mountable on an end of a multi-axis robotic arm (not shown). A roller hemming head 114 is mounted on the linear actuator 112. The linear actuator 112 provides a hemming force for performing roller hemming operations with the roller hemming head 114.

The linear actuator 112 includes a housing 116 that has an inner bore 118 that generally extends through the housing. An end cap 120 is mounted on an end of the housing 116 and closes an end of the inner bore 118. The end cap 120 may include a feature such as a mounting surface for mounting the linear actuator 112 on a robotic arm.

A pair of opposing actuator members 122 are fixedly mounted within the inner bore 118. A shaft 124 extends through the actuator members 122. A magnet 126 is mounted on the shaft 124 and is moveable within the inner bore 118. The magnet 126 is disposed between the actuator members 122. More specifically, in the first embodiment the actuator members 122 may be electromagnetic coils and the magnet 126 may be a polarized magnet having its north and south poles disposed in an axial direction relative to the shaft 124. Further, a pair of moveable yokes 128 made of a soft magnetic material sandwich the polarized magnet 126. The polarized magnet 126 and yokes 128 are fixedly mounted on the shaft 124 and are disposed between and within the electromagnetic coils 122. The magnetic field of the polarized magnet 126 forms a magnetic circuit that passes through the polarized magnet 126, the moveable yokes 128, and the electromagnetic coils 122.

An end 130 of the shaft 124 is supported by the end cap 120. For example, the end 130 may include a bushing engaged with a bushing hole 132 in an inner surface of the end cap 120. An opposite end 134 of the shaft 124 is connected to a slide 136. The slide 136 is slidable within an anti-rotate linear guide 138. The linear guide 138 is mounted on an end of the housing 116 opposite the end cap 120, and the slide 136 extends outwardly from the housing through the linear guide. The slide 136 includes an anti-rotate feature 140 such as a spline, a ball spline, a square linear bearing or similar that is cooperable with an inner surface 142 of the linear guide 138. The cooperation of the anti-rotate feature 140 and the guide inner surface 142 allows the slide to move in a linear direction along its axis in and out of the housing 116 while preventing the slide from rotating about its axis.

A distal end 144 of the slide 136 includes a connector 146 such as a quick release connector or similar. The roller hemming head 114 is connected to the slide 136 by the connector 146. For example, the connector 146 may include a through hole 148 in the slide distal end 144, and the roller hemming head 114 may be secured to the slide 136 by a fastener 150 extending through the roller hemming head 114 and the through hole in the slide 136, and a keeper 152 engaged with the fastener.

The roller hemming head 114 includes at least one hem roller, and may include a plurality of different hem rollers 154, 156 for performing different roller hemming operations. For example, one of the rollers 154 may be utilized for push-type roller hemming operations while the other roller 156 may be utilized for pull-type roller hemming operations. Also, one of the rollers 154 may be configured to fit into locations with small clearances, while the other roller 156 may be configured to hem locations having larger clearances. Further, the rollers may be configured to perform different types of hems, such as flat hems and rope hems. The hem rollers 154, 156 are mounted on the roller hemming head 114 via bearings to allow for smooth rotation of the rollers. Although, the roller hemming head 114 is shown having two hem rollers, the roller hemming head may have one roller or more than two rollers.

When current is applied to the electromagnetic coils 122, the coils are subjected to a force (in either a left or right direction as viewed in FIG. 1) that is dependent upon the direction of current flow and the resultant electromagnetic field. The electromagnetic coils 122, being fixed, do not move, and the electromagnetic field generated by the coils acts upon the moveable yokes 128 in an opposite direction, causing the moveable yokes 128 and attached shaft 124 to travel axially. The axial movement of the shaft 124 causes the slide 136 to move into or out of the housing 116. Movement of the shaft 124 to the right causes the slide 136 to move outwardly relative to the housing 116, while movement of the shaft 124 to the left causes the slide 136 to move inward. In turn, the movement of the slide 136 acts upon the connected roller hemming head 114. Outward movement of the slide 136 provides a push force when the hem roller 154 is engaged with a panel to be hemmed. Likewise, inward movement of the slide 136 provides a pull force when hem roller 156 is engaged with a panel. Further, the amount of push or pull force exerted by the hem rollers 154, 156 can be adjusted by varying the amount of current applied to the electromagnetic coils 122, which varies the amount of inward or outward force acting on the slide 136. As the magnitude of the current is increased or decreased, the hemming force also increases or decreases.

With reference to FIG. 2, in a second embodiment of the present invention a magnetically actuated roller head 210 includes a linear actuator 212 and a roller hemming head 214 mounted on the linear actuator. Reference numbers similar to those of the first embodiment indicate similar features, and unless otherwise noted below, the second embodiment has features similar to the first embodiment.

The linear actuator 212 includes a pair of opposing actuator members 258 fixedly mounted within the inner bore 218 of the housing 216. Each actuator member 258 may be an electromagnet including a cylindrical bobbin 260 mounted in the inner bore 218. A magnetic material 262 is disposed within the bobbin 260, and a coil 264 is wound on the bobbin 260. The shaft 224 extends through openings 266 in the bobbins 260 and is freely moveable therethrough. A rare earth magnet 268 is disposed between the opposing actuator members 258 and is fixed to the shaft 224. The rare earth magnet 268 is a strong, permanent magnet made from alloys of rare earth elements (lanthanides). Examples of rare earth magnets include but are not limited to neodymium magnets and samarium-cobalt magnets. The rare earth magnet 268 is polarized and has its north and south poles disposed in an axial direction relative to the shaft 224. For example, in the embodiment of FIG. 2, the north pole of the rare earth magnet 268 points to the right towards the roller hemming head 214, and the south pole points to the left towards the end cap 220 of the housing 216.

Based upon the polarity of the rare earth magnet 268, the magnetically actuated roller hemming head 210 is arranged for push type roller hemming operations in which the hem roller 254 pushes against a panel to be hemmed. Due to the strength of the magnetic field of the rare earth magnet 268, the linear actuator 212 applies approximately 330 pounds of force in a linear direction at steady state with no external power/force (zero current) applied to the actuator members 258. The actuator members 258 control and assist the actuation force of the rare earth magnet 268. More specifically, the linear force transmitted by the linear actuator 212 is adjustable in an increasing or decreasing manner by varying a current applied to the coils 264. When a current of greater than approximately 1 Amp is applied to the coils 264, the force exerted increases relative to the input value as follows: 1 Amp=360±10 pounds of force, 2 Amps=390±10 pounds of force, and 4 Amps=440±10 pounds of force. When a current of less than −1 Amp is applied to the coils 264 (i.e., less than 1 Amp in an opposite flow direction), the force exerted decreases relative to the input value as follows: −2 Amps=280±10 pounds of force, and −4 Amps=230±10 pounds of force.

Alternatively, as shown in FIG. 3, the polarity of the rare earth magnet 268 can be reversed, i.e. the rare earth magnet may be disposed such that the south pole of the rare earth magnet points to the right towards the roller hemming head 214, and the north pole points to the left towards the end cap 220 of the housing 216. In this arrangement, the magnetically actuated roller hemming head 210 is arranged for pull type roller hemming operations in which the hem roller 256 is pulled toward a panel to be hemmed. At steady state, the amount of pull force is approximately 330 pounds, and the pull force can be varied from the steady state value by application of current to the coils 264.

With reference to FIG. 4, in a third embodiment of the present invention a magnetically actuated roller head 310 includes a linear actuator 312 and a roller hemming head 314 mounted on the linear actuator. Reference numbers similar to those of the first embodiment indicate similar features, and unless otherwise noted below, the third embodiment has features similar to the first embodiment.

The linear actuator 312 includes a pair of opposing actuator members 370, 372 fixedly mounted within the inner bore 318 of the housing 316. Each actuator member 370, 372 may be a polarized rare earth magnet disposed in a non-magnetic cylindrical shell 374 that is mounted in the inner bore 318. The shaft 324 extends through openings 376 in the shell 374 and is freely moveable therethrough. A rare earth magnet 368 is disposed between the opposing actuator members 370, 372 and is fixed to the shaft 324. A gap exist between the rare earth magnet 368 and the inner bore 318 of the housing 316. The rare earth magnet 368 is polarized and has its north and south poles disposed in an axial direction relative to the shaft 324. For example, in the embodiment of FIG. 4, the north pole of the rare earth magnet 368 points to the right towards the roller hemming head 314, and the south pole points to the left towards the end cap 320 of the housing 316. Also, the north pole of the actuator member 370 points to the left and the south pole points to the right, and the north pole of the actuator member 372 points to the right and the south pole points to the left. Therefore, the polarity of the actuator member 370, rare earth magnet 368, and actuator member 372 as viewed from left to right in FIG. 4 is north-south, south-north, south-north.

Based upon the polarity of the actuator members 370, 372 and rare earth magnet 368, the magnetically actuated roller hemming head 310 is arranged for push type roller hemming operations in which the hem roller 354 pushes against a panel to be hemmed. The interactions (attraction and repulsion) of the magnetic fields of the actuator members 370, 372 and rare earth magnet 368 result in approximately 330 pounds of outward force being applied to the slide 336 and in turn the hem roller 354. The distance between the actuator members 370, 372 and the rare earth magnet 368 provides compliance for the hem roller 354 (i.e., allows the hem roller 354 to travel small distances to the left and right as viewed in FIG. 4). Also, the opposing polarities of the rare earth magnet 368 and the actuator member 372 aid in maintaining a constant hemming force through a stroke of the hem roller 354.

Alternatively, as shown in FIG. 5, the polarity of the rare earth magnet 368 can be reversed, i.e. the rare earth magnet may be disposed such that the south pole of the rare earth magnet points to the right towards the roller hemming head 314, and the north pole points to the left towards the end cap 320 of the housing 316. Therefore, the polarity of the actuator member 370, rare earth magnet 368, and actuator member 372 as viewed from left to right in FIG. 5 is north-south, north-south, south-north. In this arrangement, the magnetically actuated roller hemming head 310 is arranged for pull type roller hemming operations in which the hem roller 356 is pulled toward a panel to be hemmed. The amount of pull force is approximately 330 pounds, and the opposing polarities of the rare earth magnet 368 and the actuator member 370 aid in maintaining a constant hemming force through a stroke of the hem roller 356.

In the third embodiment, the housing 316 and shaft 324 may be non-magnetic so as to not interfere or interact with the magnetic field of the rare earth magnets.

Although the invention has been described by reference to specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims.

Claims

1. A magnetically actuated roller head comprising:

a linear actuator mountable on an end of a multi-axis robotic arm;

said linear actuator including a slide, a magnet operably connected to said slide and operable to urge said slide in a linear direction, and a connector disposed on a distal end of said slide; and

a roller hemming head mounted on said linear actuator by said connector, said roller hemming head including at least one hem roller.

2. The magnetically actuated roller head of claim 1, wherein said magnet is a rare earth magnet.

3. The magnetically actuated roller head of claim 1, wherein said linear actuator includes a rare earth magnet disposed between two opposing magnets, the polarity of one of said opposing magnets is disposed in the same direction as the polarity of said rare earth magnet and the polarity of the other of said opposing magnets is disposed in an opposite direction to the polarity of said rare earth magnet.

4. The magnetically actuated roller head of claim 3, wherein said two opposing magnets are rare earth magnets.

5. The magnetically actuated roller head of claim 1, wherein said linear actuator includes an electromagnet disposed on each of opposite sides of said magnet, said electromagnets controlling and assisting a force transmitted by said magnet.

6. The magnetically actuated roller head of claim 1, wherein said slide includes an anti-rotate feature.

7. A magnetically actuated roller head comprising:

a housing including an internal bore, said housing being mountable on an end of a multi-axis robotic arm;

a pair of opposing actuator members fixedly mounted within said inner bore;

a shaft extending through said actuator members;

a magnet mounted on said shaft and moveable within said inner bore, said magnet being disposed between said actuator members;

a slide connected to said shaft and extending outwardly from said housing;

a connector disposed on a distal end of said slide; and

a roller hemming head mounted on said connector, said roller hemming head including at least one hem roller;

whereby said actuator members control and assist a hemming force applied by said roller hemming head through said magnet.

8. The magnetically actuated roller head of claim 7, wherein said magnet is a rare earth magnet.

9. The magnetically actuated roller head of claim 7, wherein said actuator members are rare earth magnets.

10. The magnetically actuated roller head of claim 9, wherein the polarity of one of said actuator members is disposed in the same direction as the polarity of said rare earth magnet and the polarity of the other of said actuator members is disposed in an opposite direction to the polarity of said rare earth magnet.

11. The magnetically actuated roller head of claim 7, wherein said actuator members are electromagnets.

12. The magnetically actuated roller head of claim 7, wherein said housing includes an anti-rotate linear guide, and said slide includes an anti-rotate feature cooperable with said linear guide.

13. The magnetically actuated roller head of claim 12, wherein said anti-rotate feature is one of a spline, a ball spline, and a square linear bearing.

14. A method of roller hemming comprising the steps of:

mounting a linear actuator on an end of a multi-axis robotic arm, said linear actuator including a slide, a magnet operably connected to said slide and operable to urge said slide in a linear direction, and a connector disposed on a distal end of said slide; and

mounting a roller hemming head on said linear actuator by said connector, said roller hemming head including at least one hem roller;

whereby said linear actuator provides a hemming force for performing roller hemming operations with said hem roller.

15. The method of claim 14, wherein said magnet is a rare earth magnet.

16. The method of claim 14, including the step of:

disposing said magnet between a pair of opposing actuator members.

17. The method of claim 16, wherein said actuator members are rare earth magnets.

18. The method of claim 16, wherein said actuator members are electromagnets.

19. The method of claim 14, including the step of:

restricting axial rotation of said roller hemming head by providing a spline on said slide.

20. The method of claim 14, including the step of:

providing a plurality of different hem rollers on said roller hemming head.